Making a leap means different things for different MLB players.

Some players go from being ineffective to at least replacement-level. Some go from good to All-Star. Some regain their star status after underperforming. And some just make it back to their previous form after injuries derailed them.

With that in mind, here's a look at the player who has made the biggest leap for all 30 MLB teams so far this season.

Arizona Diamondbacks: Closer Paul Sewald

Between 2021 and 2023, Paul Sewald posted a 2.95 ERA and recorded 65 saves with the Seattle Mariners and Arizona Diamondbacks. While he had a 5.40 ERA in the postseason last year, Sewald was part of an Arizona bullpen that helped the team win only the second NL pennant in franchise history.

So, it's not as though Sewald has come out of nowhere. But at age 34, he's gone from being a solid reliever to one of the best MLB has to offer.

Sewald missed all of April with a left oblique strain. Since returning, he has allowed only one earned run over 16 relief appearances. He's converted all 10 of his save attempts.

Sewald can become a free agent after this season, so if the Snakes don't turn around what's been a disappointing year, contenders should be lined up to try to trade for him.

Atlanta Braves: RHP Reynaldo López

The Atlanta Braves raised eyebrows when they signed Reynaldo López to a three-year, $30 million deal this past offseason after he split the 2023 campaign as a reliever with the Chicago White Sox, Los Angeles Angels and Cleveland Guardians.

A few months into the deal, it looks like the latest stroke of genius from president of baseball operations Alex Anthopoulos.

Across 14 starts this season, López has a 1.70 ERA and 81 strikeouts. His single-season career high in WAR came when he posted a 2.4 mark for the White Sox in 2019. He already has a 2.2 WAR in 2024, per FanGraphs.

The 30-year-old has already logged more innings this year than he's had since 2019, so it will be interesting to see how he holds up as the season goes along.

However, he's one of the biggest reasons the Braves have been able to withstand the loss of NL Cy Young Award candidate Spencer Strider.

Baltimore Orioles: 3B Jordan Westburg

Jordan Westburg posted a 100 OPS+ in 68 games for the Orioles last year, meaning he was a league average player.

However, the 25-year-old has a 145 OPS+ in nearly half a season this year, making him another emerging star in an organization overflowing with position-playing talent.

A first-round pick in 2020, Westburg has already homered 13 times this season. His .853 OPS is second on the Orioles, trailing only AL MVP candidate Gunnar Henderson.

What's more, while Westburg has also seen time at second base, he's shined as the primary third baseman for the O's, with four defensive runs saved and five outs above average.

Boston Red Sox: RHP Tanner Houck

Tanner Houck posted a 5.01 ERA and 4.43 FIP across 21 starts in 2023, which is rather underwhelming production for the right-hander.

In 2024, he's been anything but underwhelming. As of writing, the 28-year-old led pitchers with a 2.21 FIP and a 3.6 WAR, per FanGraphs. He also has the top mark among AL pitchers in ERA (2.18), ERA+ (195) and HR/9 (0.2).

Right now, Houck should be at the forefront of the conversation for who should get the ball for the AL to start the All-Star Game. It's been quite the breakout for the 2017 No. 24 overall pick.

Chicago White Sox: RHP Erick Fedde

Erick Fedde has had a winding path to the White Sox, with whom he signed a two-year, $15 million deal with after winning MVP in the KBO League last year.

That journey may land him on a new team before the trade deadline because he's pitched so well in his first season back stateside.

Across 17 starts this season, the 31-year-old has a 3.23 ERA and 3.58 FIP. Mind you, this is someone who still had a relatively limited market last winter despite his success in South Korea because he had posted a 5.41 ERA and 5.17 FIP over parts of six seasons with the Washington Nationals.

However, the 2014 first-round pick is having the finest season of his MLB career thus far. And some contending team is going to be lucky to get Fedde at a very affordable rate for two pennant races.

Chicago Cubs: 1B Michael Busch

With Freddie Freeman at first base and Shohei Ohtani at DH, Michael Busch didn't have a path to playing time with the Los Angeles Dodgers.

So, the Cubs traded for the former first-round pick in January, and they've had a tremendous return so far.

On a team that's had disappointing results from Dansby Swanson, Christopher Morel and Nico Hoerner at the plate, Busch has been one of the better offensive players.

The 26-year-old has homered nine times, driven in 28 runs and posted a .795 OPS that's second on the team only to Seiya Suzuki.

Busch's presence wouldn't preclude the Cubs from trying to sign someone like Pete Alonso this upcoming winter, though.

The former Dodgers player has graded out well defensively at first base, with three defensive runs saved and four outs above average, but he could shift to DH to make room for a major addition.

Given Busch won't even become eligible for arbitration until the 2027 season, there would also be quite a bit of trade interest in him if the Cubs upgraded in the winter.

Cincinnati Reds: RHP Hunter Greene

Hunter Greene may still not be a finished product, but he's taken a big step forward in 2024.

His ERA has dropped more than a run from a year ago, going from 4.82 over 22 starts in 2023 to 3.79 across 16 games this season. His 103 strikeouts put him among the top seven pitchers in the NL as well.

The 24-year-old still has hit 11 batters and issued 39 walks, so there's more work to be done. But there's never been a question about his stuff, and it feels like he's growing as a pitcher.

Cleveland Guardians: C/IF/OF David Fry

In 2023, the Cleveland Guardians finished 27th in baseball with a .695 OPS. Without making a major offseason addition, they have jumped to 11th in team OPS in 2024 with a .729 mark.

David Fry is hardly the only reason for that, but he posted a .734 OPS in his first 57 MLB games a year ago. Across the first 59 games of the 2024 season, he has a .931 OPS.

The 28-year-old doesn't quite have enough at-bats to be a qualified hitter, but if he did, his OPS would be among the 10-best marks in baseball.

Specifically, Fry has mashed left-handed pitchers, with a .338 batting average and 1.153 OPS.

He's also provided first-year manager Stephen Vogt with tremendous defensive flexibility, taking down time at catcher, first base, third base and all three outfield positions this year.

Fry is a late bloomer, but he sure has bloomed.

Colorado Rockies: RHP Cal Quantrill

Few pitchers land with the Rockies and revive their careers, but that's just what Cal Quantrill has done.

The 29-year-old was very effective for Cleveland between 2021 and 2022, going 23-8 with a 3.16 ERA across 72 games, 54 of which were starts.

However, he posted an unsightly 5.24 ERA over 19 starts for the Guardians last season, and he was designated for assignment in November.

Rockies general manager Bill Schmidt acquired him in what seemed a fairly inconsequential trade last November, and Quantrill has repaid that decision by posting a 3.50 ERA over 16 starts this season.

Quantrill hasn't been disastrous at Coors Field, as he has a 4.05 ERA in seven home starts this year. But he has been nearly a run better on the road, with a 3.06 ERA in nine starts.

He has one remaining year of arbitration eligibility, but the Rockies might be wise to cash him in via trade this summer. Certainly, there will be interest in acquiring him for two playoff runs.

Detroit Tigers: RHP Jack Flaherty

In 2019, Jack Flaherty led the NL in WHIP (0.968) and H/9 (6.2), en route to finishing fourth in Senior Circuit Cy Young voting as a member of the St. Louis Cardinals. He looked like one of the most promising young pitchers in baseball.

The 28-year-old has gone off-kilter the last few seasons, posting a 4.99 ERA across 144.1 innings pitched in 2023, a campaign that he split between the Cardinals and Orioles.

However, Tigers president of baseball operations Scott Harris gambled on Flaherty in the offseason with a one-year, $14 million deal.

Detroit hit big on that gamble, as Flaherty has a 3.24 ERA, 1.000 WHIP and 115 strikeouts over 15 starts this season. He's made quite the No. 2 behind ace Tarik Skubal.

The Tigers aren't ready to compete yet, which may mean Flaherty becomes a trade piece in the coming weeks. But there's also an argument for trying to sign him to a long-term extension.

Houston Astros: RHP Ronel Blanco

Justin Verlander and Framber Valdez have both spent time on the injured list this season, while José Urquidy and Cristian Javier have been lost for the season after undergoing Tommy John surgery earlier this month.

In a year without a ton of pitching stability, Ronel Blanco has been the best starter for first-year skipper Joe Espada. He threw a no-hitter in his first start of the season, but he's hardly been a one-hit wonder. He has a 2.34 ERA across 14 starts this season.

Blanco has a 4.07 FIP and has already logged 84.2 innings this year after pitching a total of 125.1 innings between Triple-A and the majors last season.

We'll see whether the 30-year-old is able to sustain his success in the second half of the season, but he's been able to keep them afloat in the first half.

Kansas City Royals: LHP Ángel Zerpa

Admittedly, the Kansas City Royals don't have a great candidate here, as Cole Ragans' transformation into an ace is a carryover from last year.

However, reliever Ángel Zerpa has a 3.41 ERA over 35 appearances this season, which is a big improvement from the 4.85 ERA he posted across 42.2 innings for the team last season.

What's clear here is that while the Royals have great one-two punches in their rotation (Ragans and Seth Lugo) and lineup (Salvador Perez and Bobby Witt Jr.), general manager J.J. Picollo needs to make some significant additions for them to return to the postseason for the first time since 2015.

Los Angeles Angels: LHP Tyler Anderson

Tyler Anderson was an All-Star with the Los Angeles Dodgers in 2022, which earned him a three-year, $39 million deal in free agency ahead of the 2023 campaign from the pitching-desperate Angels.

The 34-year-old struggled in his first season with the Angels, though, posting a 5.43 ERA and 4.92 FIP over 141 innings.

However, the second season with the Halos has gone much better, as he has a 2.63 ERA in 16 starts this season. The 4.77 FIP he's posted leaves you to wonder if regression is coming, but so far he has gotten excellent results.

The Angels signed Anderson in an attempt to salvage the Shohei Ohtani/Mike Trout era, which was already a lost cause.

Now that Anderson is pitching well again, general manager Perry Minasian might be wise to offload the remainder of his contract and hope to get a lottery ticket that becomes a winner once scratched off in return.

Los Angeles Dodgers: LHP Alex Vesia

In some ways, this is more of a bounce-back season than anything because Alex Vesia posted a 2.19 ERA between 2021 and 2022.

However, relative to the pitcher who posted a 4.35 ERA across 56 games a season ago, the 2024 iteration of Vesia has taken quite the leap. In 34 outings this season, he has a 1.26 ERA and a WHIP under 0.9.

The 28-year-old will be an important pitcher in the postseason as the Dodgers try to navigate around left-handed hitters such as Bryce Harper, Matt Olson and Kyle Schwarber.

In 2024, though, he's been even more dominant against right-handed hitters, who have managed to hit just .103 with a .465 OPS against him.

So, come October, manager Dave Roberts will be able to deploy Vesia in all sorts of high-leverage pockets.

Miami Marlins: RHP Declan Cronin

Virtually everything that could go wrong for the Miami Marlins in terms of their pitchers has done this season.

However, reliever Declan Cronin is one of the few silver linings for the Fish.

The 26-year-old posted a 9.00 ERA in nine relief appearances for the White Sox last season. They were one of two teams that designated him for assignment this past winter—the Houston Astros being the other—with the player ultimately finding a home in Miami in February.

While Cronin began the season with the Triple-A Jacksonville Jumbo Shrimp, he has been very good since being recalled in mid-April, posting a 2.95 ERA over 36.2 innings out of the bullpen.

With closer Tanner Scott likely to be traded this summer, the Marlins could keep Cronin and try to make him one of their long-term anchors in the bullpen.

What's also possible, though, is that president of baseball operations Peter Bendix tries to sell high on Cronin, who won't even be arbitration-eligible until 2027.

Milwaukee Brewers: LHP Bryan Hudson

The Brewers have been without All-Star closer Devin Williams for the whole season so far, but manager Pat Murphy's group has still been one of the better relief units in baseball.

Trevor Megill has stepped in and been excellent as the team's closer, while Jared Koenig has also been a valuable Swiss Army knife out of the bullpen.

Still, it's the transformation of lefty Bryan Hudson that has been the biggest development for the bullpen.

Acquired in a January trade after the Los Angeles Dodgers designated him for assignment, he had a 7.27 ERA to show for just six MLB relief appearances a year ago.

Granted, the 27-year-old has been effective at Triple-A Oklahoma City for the Dodgers last year, so it's not as though it would have been a complete shock for him to be throwing the ball well at the MLB level in 2024.

But he's been downright dominant for the Brew Crew this season, with a 0.84 ERA to show for 27 relief appearances. He's been equally effective against hitters from both sides of the plate, as lefties are hitting .130 against him, as opposed to .137 from righties.

Milwaukee's starting rotation has serious questions that general manager Matt Arnold has to address before the July 30 trade deadline.

If Williams returns from the stress fractures in his back after the All-Star Break, though, this might be the most dominant bullpen in baseball.

Minnesota Twins: RHP Jorge Alcalá

Third baseman José Miranda and reliever Griffin Jax deserve to be mentioned here, as they've both had tremendous seasons for the Twins thus far.

But reliever Jorge Alcalá has, out of the blue, had an incredible campaign for Minnesota.

The 28-year-old had spent parts of five seasons with the Twins prior to 2024, posting a 3.86 ERA and 4.44 FIP across 90 largely unremarkable outings.

But over his first 22 appearances out of manager Rocco Baldelli's bullpen this year, Alcalá has a 2.03 ERA, and his 2.97 FIP doesn't suggest he's someone whose results are going to crater as the season goes along even if his performance dips a bit.

With a four-pitch mix that leans heavily on a 97 mph fastball and a slider that averages nearly 90 mph, Alcalá has been one of the most positive relief developments in baseball this season.

If the Twins can get closer Jhoan Duran back on track, they're going to have a fairly nasty relief trio with him, Alcalá and Jax.

New York Yankees: RHP Luis Gil

Even after giving up seven runs in just 1.1 innings of work against the Orioles on June 20, Luis Gil still finds himself at the forefront of the races for both the AL Rookie of the Year and AL Cy Young Award.

With just seven MLB starts on his resume before this season—none of which came in 2023—his transformation into an ace was hard to see coming. But he has a 9-3 record with a 3.15 ERA and 3.63 FIP over 16 starts this season. He's almost certainly going to be an All-Star.

At some point this season, Gil is likely going to have to pitch out of the bullpen, as the Yankees protect the veteran's long-term health.

However, the 26-year-old has made himself a crucial piece for the Yankees both in the short and long term.

New York Mets: 3B Mark Vientos

Inconsistent output from the since-optioned Brett Baty gave Mark Vientos the chance to grab the third base job in New York and run with it, and that's exactly what he's done.

In just over a month's worth of games, the 24-year-old has nine home runs, six doubles and a .928 OPS. But he did hit .211 with a .620 OPS in 65 games for the Mets a season ago.

Vientos has graded out as slightly below average at the hot corner, with -2 defensive runs saved and -1 outs above average, though it's hard to put too much stock in those metrics after a month.

What is interesting is the possibility of him shifting across the diamond and playing first base if Pete Alonso is either traded this summer or departs in free agency in the offseason. That would open the door for the Mets to continue giving Baty a look or to pursue a star third baseman.

Oakland Athletics: OF JJ Bleday

After being acquired in the February 2023 trade that sent LHP A.J. Puk to the Miami Marlins, JJ Bleday hit .195 with just a .666 OPS over 82 games in his first season with the Athletics.

In a near-identical sample size this season, Bleday has improved massively as he is among the AL lead with 22 doubles, having homered 11 times. He's going to have to beat out Brent Rooker, but he is a candidate to be the lone All-Star for the A's.

Bleday is still only 26 and won't become arbitration-eligible until the 2026 campaign. The 2019 No. 4 overall pick is definitely going to Sacramento with the A's for the next three seasons, and perhaps he'll still be with the team if they do ultimately relocate to Las Vegas.

Philadelphia Phillies: LHP Ranger Suárez

Third baseman Alec Bohm, starter Cristopher Sánchez and relievers Matt Strahm and Jeff Hoffman all have a chance to be All-Stars for the first time, and they are worthy candidates.

Still, Ranger Suárez is the easy choice here.

Not only is he on track to be an All-Star for the first time, but he's also the likely front-runner to start the game for the NL.

Across 51 starts between 2022 and 2023, the always-cool lefty posted matching 3.88 marks in terms of ERA and FIP, making him a strong No. 3 behind Zack Wheeler and Aaron Nola.

The 28-year-old has effectively pitched out of the bullpen, including when he closed out an NL pennant for the Phillies in 2022.

Still, Suárez has stepped out of the shadows of some of his rotation mates this year and pitched like an ace. He currently leads baseball in both ERA (1.83) and ERA+ (203).

It's still early, but the lefty has jumped into the NL Cy Young race and put himself in position to earn a lucrative deal when he become a free agent after the 2025 season, if the Phillies don't extend him sooner.

Pittsburgh Pirates: LHP Bailey Falter

The Pirates bought low on Bailey Falter last July, acquiring him in a swap for utility man Rodolfo Castro.

Falter was 0-7 with a 5.13 ERA for the Phillies before the trade and an obvious change-of-scenery candidate.

The 27-year-old struggled across 10 appearances—seven of which were starts—with the Pirates in 2023, posting a 5.58 ERA. But the lefty has a 4.00 ERA over 15 starts this season, making him a capable No. 4 starter behind the exciting trio of Paul Skenes, Jared Jones and Mitch Keller.

It's at least mildly concerning that Falter has a 4.53 FIP, which suggests some regression could be coming. But so far, he has gotten respectable results for the Pirates, who have him under team control through the 2028 season.

San Diego Padres: LF Jurickson Profar

Most of the players on this list tend to be under 30, and some of them were relatively unknown nationally entering the season. But Jurickson Profar—a 31-year-old in his 11th season—doesn't fit that description.

However, the former top prospect is putting together the finest campaign of his career, and it's definitely a major improvement over what he did a year ago.

Last season with the Rockies, Profar posted a .680 OPS in 111 games before being released in late August. He returned to the Padres, where he had spent the previous three seasons, for 14 games in September.

That was enough for San Diego to give him an MLB deal in the offseason, which guaranteed him just $1 million and looks like being one of the best contracts of the winter.

While Ha-Seong Kim and Manny Machado have underwhelmed at the plate, Profar has helped to keep the Padres in the NL wild-card race by hitting .316 with an .893 OPS.

His defensive metrics in left field are below average, but he's done enough with his bat to have a real shot to make his first All-Star appearance on July 16.

San Francisco Giants: OF Heliot Ramos

A first-round pick by the Giants in 2017, Heliot Ramos hit just .158 in 34 MLB at-bats between 2022 and 2023. He even spent the first month of the 2024 season at Triple-A Sacramento.

But after homering eight times in 30 games at Triple-A, Ramos was recalled in May, and he hasn't looked back since. In less than 50 games with the Giants, he has already slugged 10 home runs and posted 35 RBI.

The 24-year-old has also given the Giants defensive flexibility, playing all three outfield positions and posting seven defensive runs saved between left field and right field.

His emergence feels especially important with center fielder Jung Hoo Lee lost for the season due to a dislocated left shoulder.

Since the departure of Barry Bonds, this is a team that's been desperate for consistent thump. Ramos has shown enough to think he could provide that over the long run while also giving manager Bob Melvin greater options because he can play all three outfield spots.

Seattle Mariners: RHP Bryan Woo

Bryan Woo posted a 4.21 ERA over his first 18 MLB starts a year ago, giving the Mariners hope that they had found another consistent rotation contributor on a staff that already included Luis Castillo, Logan Gilbert, George Kirby and Bryce Miller.

Seattle got a scare when Woo missed the first six weeks of the season with inflammation in his pitching elbow, but he has been lights-out since returning from the injured list.

Across eight starts this season, Woo is 3-1 with a 1.67 ERA and minuscule 0.689 WHIP.

We've written at length about the need for Seattle president of baseball operations Jerry DiPoto to upgrade one of the league's poorer lineups. If he's able to do that in advance of the trade deadline, the Mariners could be World Series contenders with Woo and this starting rotation.

St. Louis Cardinals: SS Masyn Winn

So many of the notable players on the Cardinals roster—such as Nolan Arenado, Paul Goldschmidt and Sonny Gray—are in their mid-30s. So, it's encouraging to see a player like Masyn Winn, who could be one of the faces of the team for the next decade.

The 22-year-old has a cannon arm at shortstop, and he is currently tied for the most defensive runs saved among players at his position with seven.

Additionally, after posting just a .467 OPS in his first 37 MLB games a year ago, Winn has fared much better at the plate this season. He's hitting .288 with 27 RBI and a .751 OPS in his first full MLB campaign. When paired with his glove, his step forward offensively is super-exciting.

Tampa Bay Rays: C Ben Rortvedt

The Tampa Bay Rays don't necessarily have an obvious candidate here, as their starting rotation has been crushed by injuries, while Yandy Díaz and Randy Arozarena have underperformed offensively.

So, here's a bit of love for catcher Ben Rortvedt. He's got 23 RBI and a 111 OPS+—100 is the league average—in 56 games for the Rays this season. He also has two defensive runs saved and a 3.0 framing grade, so he's been a net positive behind the plate.

The 26-year-old has previously spent time with the Twins and Yankees, but he appears to have found a home in Tampa.

Texas Rangers: 3B Josh Smith

Texas has been without third baseman Josh Jung since he fractured his right wrist in early April.

The World Series champions have had a hangover this year, but Josh Smith stepping up in Jung's absence has been one of the most positive notes.

Acquired in the July 2021 trade that sent Joey Gallo to the Yankees, Smith has turned into a key cog for the Rangers in 2024. He is hitting .298 with an .858 OPS.

On a team full of stars, it's Smith who leads Texas in WAR this season at 2.6.

The 26-year-old has experience playing both shortstop and second base, but neither of those spots is available in Texas.

So, manager Bruce Bochy will have to get creative in finding at-bats for Smith once Jung returns at third base. That will likely mean more time in left field in the absence of rookie Evan Carter.

Fortunately, Smith already has four defensive runs saved in just over 100 innings in left field this season, so he's shown the potential to be a super-utility star.

Toronto Blue Jays: RHP Trevor Richards

The Toronto Blue Jays have been one of baseball's most disappointing teams in 2024, and they would have far more candidates if this list was ranking players who have regressed this year.

With that said, one of the few bright spots in an otherwise disastrous bullpen is Trevor Richards. Between 2022 and 2023, he posted a 5.14 ERA over 118 outings, 111 of which came in relief. But in 33 games this year, he has a 2.63 ERA and 3.65 FIP.

The 31-year-old righty can become a free agent after the season, so he's likely to move this summer if the Blue Jays don't rebound.

Contenders looking for a reliever capable of taking down multiple innings, potentially as an opener, will be intrigued by Richards.

Washington Nationals: RHP Dylan Floro

The most encouraging long-term development for the Nationals is that shortstop CJ Abrams' bat has taken a major step forward in 2024, and either he or RHP Jake Irvin could have been the pick here.

But one of the reasons that the Nationals are alive in the NL wild-card race is that they hit on a few veteran bounce-back signings.

Outfielder Jesse Winker gets the bulk of the attention in that regard, but reliever Dylan Floro—who signed for just $2.25 million this past offseason—is having a career year in his ninth MLB season.

The 33-year-old split last season with the Marlins and Twins, posting an unsightly 4.54 ERA across 62 games. Through 39 games this year, he has a 2.14 ERA.

If the Nationals fall out of contention, he'll be a coveted trade candidate. But if Floro keeps pitching this well, Washington general manager Mike Rizzo may add before the trade deadline.