As the calendar gets set to flip to September, it's time for another update to our monthly MLB rookie rankings.

Pittsburgh Pirates pitcher Paul Skenes and San Diego Padres outfielder Jackson Merrill remain the clear top dogs in this year's rookie crop, but there has been plenty of shuffling behind them in recent weeks.

New York Yankees catcher Austin Wells and Milwaukee Brewers outfielder Jackson Chourio have raised their stock considerably with strong second-half showings, and that is reflected in their significant climb up the rankings this time around.

Future expectations, long-term upside, preseason prospect rankings and minor-league track records were not a factor in these rankings. The sole focus of these rankings is on each player's overall 2024 production at the MLB level.

Honorable Mentions (Hitters)

These hitters all made our preliminary list, but fell short of cracking the final Top 25:

OF Lawrence Butler, OAK
3B Junior Caminero, TB
OF Pete Crow-Armstrong, CHC
C Adrian Del Castillo, ARI
2B Nick Gonzales, PIT
2B/SS David Hamilton, BOS
C Iván Herrera, STL
OF Rece Hinds, CIN
1B/2B Spencer Horwitz, TOR
2B Colt Keith, DET
OF Heston Kjerstad, BAL
OF Wyatt Langford, TEX
C Korey Lee, CWS
IF Nick Loftin, KC
1B/OF Joey Loperfido, HOU/TOR
C Kyle McCann, OAK
OF Parker Meadows, DET
OF Andy Pages, LAD
C Pedro Pagés, STL
OF Wenceel Pérez, DET
SS Brayan Rocchio, CLE
1B Nolan Schanuel, LAA
IF/OF Daniel Schneemann, CLE
SS Max Schuemann, OAK
OF Michael Siani, STL
IF Weston Wilson, PHI

Honorable Mentions (Pitchers)

These pitchers all made our preliminary list, but fell short of cracking the final Top 25:

SP Spencer Arrighetti, HOU
SP Valente Bellozo, MIA
SP Hayden Birdsong, SF
RP Spencer Bivens, SF
SP/RP Ben Brown, CHC
RP Cam Booser, BOS
SP/RP José Buttó, NYM
SP Jonathan Cannon, CWS
SP/RP Cooper Criswell, BOS
RP Declan Cronin, MIA
RP Hans Crouse, LAA
SP Joey Estes, OAK
RP Tyler Ferguson, OAK
RP Ryan Fernandez, STL
SP Robert Gasser, MIL
SP Kyle Harrison, SF
RP Tim Herrin, CLE
SP DJ Herz, WAS
RP Porter Hodge, CHC
SP/RP Grant Holmes, ATL
RP Bryan Hudson, MIL
RP Bryce Jarvis, ARI
SP Jared Jones, PIT
RP Orion Kerkering, PHI
RP Bryan King, HOU
SP Landon Knack, LAD
RP Jacob Latz, TEX
RP Kyle Leahy, STL
RP Luke Little, CHC
RP Yuki Matsui, SD
RP Erik Miller, SF
RP Kyle Nicolas, PIT
RP Dedniel Núñez, NYM
SP Mitchell Parker, WAS
RP Randy Rodríguez, SF
SP Yariel Rodríguez, TOR
SP River Ryan, LAD
RP Eduardo Salazar, LAD/WAS
SP Christian Scott, NYM
RP Justin Slaten, BOS
SP/RP Mitch Spence, OAK
RP Hunter Stratton, PIT
SP Randy Vásquez, SD
RP Victor Vodnik, COL
SP Matt Waldron, SD
RP Danny Young, NYM

The Mason Miller Question

Is Mason Miller a rookie?

According to the rookie leaderboards at MLB.com and FanGraphs, he is part of this year's rookie class, but a quick look at his Baseball Reference page reveals the following line:

• "Exceeded rookie eligibility limits during 2023 season"

The confusion seems to stem from how many days of service time he accrued last year while spending roughly four months on the injured list, and whether his retroactive placement on the injured list to May 8 meant that May 8 counted as a day of service time or not.

It's a convoluted situation that could be easily resolved with one quick press release from Major League Baseball, but to this point that has not happened.

There is some precedent here, as Keibert Ruiz was thought to be rookie-eligible heading into the 2022 season and Vegas sportsbooks were even actively taking bets on him early in the season, only for it to eventually be clarified that he had exceeded rookie limits the previous year based on active service time.

Baseball Reference had it right from the start in that case, so I'm inclined to believe there is a reason they still have not altered that line on Miller's page.

For now, I'll continue to work under the assumption that he is not rookie eligible.

If he was, he would slot into the top 10 in these rankings.

Nos. 25-21

25. OF James Wood, Washington Nationals

Stats: 50 G, 130 OPS+, .275/.374/.429, 15 XBH (5 HR), 30 RBI, 0.8 WAR

Wood looks the part of a future middle-of-the-order star, settling in nicely as the Nationals everyday left fielder since making his MLB debut on July 1. The 21-year-old has a lot to live up to as the prospect centerpiece of the blockbuster deal that sent Juan Soto to the San Diego Padres at the 2022 deadline, but he is off to a nice start.

24. SS Xavier Edwards, Miami Marlins

Stats: 47 G, 138 OPS+, .349/.428/.436, 11 XBH (1 HR), 17 RBI, 22 SB, 2.0 WAR

A Top 100 prospect prior to the 2020 season when he was still a member of the Padres organization, Edwards was traded twice before finding a regular role with the Marlins this season. He took over as the team's starting shortstop after veteran Tim Anderson was cut loose, and while he has bottom-of-the-scale power, his contact skills and elite speed have been on full display.

23. RP Justin Martinez, Arizona Diamondbacks

Stats: 50 G, 6 SV, 8 HLD, 2.02 ERA, 1.24 WHIP, 11.2 K/9, 58.0 IP, 1.8 WAR

Armed with a high-octane sinker that averages 100.1 mph and a splitter that has generated a 52.7 percent whiff rate, there is no question Martinez has late-inning stuff, and the D-backs turned to him to close games when Paul Sewald hit a rough patch. The 23-year-old was signed for just $50,000 out of the Dominican Republic in 2018, and at the time he was relatively new to pitching having just moved to the mound after previously playing in the outfield.

22. OF Jhonkensy Noel, Cleveland Guardians

Stats: 43 G, 154 OPS+, .254/.326/.602, 17 XBH (12 HR), 23 RBI, 1.1 WAR

Is there a better nickname in baseball right now than the one given to the hulking 6'3", 250-pound Noel? "Big Christmas" has long been one of baseball's best power-hitting prospects with a 32-homer season in 2022 and a 27-homer follow-up in 2023, but the question has always been whether he would make enough contact to utilize that power. The 23-year-old is striking out at a 31.1 percent clip in his first big-league action, but that hasn't stopped him from launching 12 home runs in 132 plate appearances.

21. SP Yoshinobu Yamamoto, Los Angeles Dodgers

Stats: 14 GS, 2.92 ERA (137 ERA+), 1.07 WHIP, 17 BB, 84 K, 74.0 IP, 1.7 WAR

Yamamoto has not pitched since June 15 when he left his start against the Kansas City Royals after just two innings with what turned out to be a rotator cuff strain. He began a rehab assignment at Triple-A on Wednesday and will likely make at least one more start before the team considers activating him, but the bigger goal will be getting him ready for the postseason.

Nos. 20-16

20. 3B Joey Ortiz, Milwaukee Brewers

Stats: 111 G, 104 OPS+, .243/.341/.398, 31 XBH (9 HR), 45 RBI, 7 SB, 2.2 WAR

Ortiz was part of the NL Rookie of the Year race over the first two months of the season, but his production has dipped. Since the start of July, he is hitting .191/.275/.305 with just nine extra-base hits in 149 plate appearances, and he has been moved down to the No. 9 spot in the batting order. The 26-year-old still has an extremely bright future, though, and he could take over at shortstop next year if Willy Adames walks in free agency.

19. SP Spencer Schwellenbach, Atlanta Braves

Stats: 15 GS, 3.72 ERA (112 ERA+), 1.07 WHIP, 18 BB, 102 K, 87.0 IP, 1.7 WAR

The No. 5 spot in the Atlanta rotation was a revolving door until Schwellenbach made his MLB debut on May 29, and he has settled in nicely as the season has progressed. Since the start of July, he has a 2.60 ERA, 0.94 WHIP and 70 strikeouts in 55.1 innings with seven quality starts in nine outings. The 24-year-old's emergence has given the team a rotation building block heading into an offseason where Max Fried and Charlie Morton are both free agents.

18. IF/OF Ceddanne Rafaela, Boston Red Sox

Stats: 129 G, 90 OPS+, .259/.290/.404, 37 XBH (13 HR), 61 RBI, 17 SB, 2.5 WAR

While the .290 on-base percentage and 3.1 percent walk rate leave a lot to be desired, Rafaela has been an extremely valuable player for the Red Sox this season. The 23-year-old has provided some thump at the bottom of the lineup while playing elite defense in center field and filling in capably over 578 innings of action at shortstop. The eight-year, $50 million extension he signed in April looks like a shrewd move by the Boston front office.

17. OF Jacob Young, Washington Nationals

Stats: 122 G, 87 OPS+, .255/.314/.338, 25 XBH (3 HR), 30 RBI, 30 SB, 2.8 WAR

Chicago Cubs rookie Pete Crow-Armstrong has received plenty of hype thanks to his highlight-reel defense and top-of-the-scale speed, but Young has essentially the same toolbox and has been the far more productive rookie. His 12 Defensive Runs Saved rank fifth among all outfielders and his 30 steals are good for fourth on the NL leaderboard.

16. SP Simeon Woods Richardson, Minnesota Twins

Stats: 23 GS, 3.85 ERA (109 ERA+), 1.18 WHIP, 38 BB, 102 K, 117.0 IP, 2.1 WAR

After making a single spot start in 2022 and 2023, Woods Richardson has broken through to shore up the back of the Minnesota rotation and help ease the loss of Sonny Gray in free agency. The 23-year-old has been a high-ceiling prospect since he was taken in the second round of the 2018 draft, and the Twins acquired him along with Austin Martin in the deal that sent José Berríos to Toronto at the 2021 trade deadline.

Nos. 15-11

15. C Austin Wells, New York Yankees

Stats: 91 G, 116 OPS+, .256/.347/.426, 25 XBH (10 HR), 38 RBI, 2.3 WAR

It's been a tale of two seasons for Wells in his first year as the Yankees starting catcher.

• 1st Half: 194 PA, .216/.309/.377, 15 XBH (6 HR), 20 RBI
• 2nd Half: 124 PA, .320/.407/.505, 10 XBH (4 HR), 18 RBI

The 25-year-old has clearly turned a corner, and while he might climb all the way to the top of the AL Rookie of the Year race, he has as much upward momentum as anyone in these rankings.

14. SP Tobias Myers, Milwaukee Brewers

Stats: 20 GS, 2.99 ERA (142 ERA+), 1.13 WHIP, 28 BB, 94 K, 108.1 IP, 2.1 WAR

Before this year, Myers was best known as the pitcher the Rays gave up to acquire a young Junior Caminero from Cleveland prior to the 2022 season. He also spent time with the Giants and White Sox before landing in Milwaukee prior to last year. The 26-year-old has held down a rotation spot for 20 starts, and while his 4.15 FIP speaks to some regression to come, he has been an invaluable piece of the puzzle for the NL Central leaders.

13. OF Wilyer Abreu, Boston Red Sox

Stats: 104 G, 128 OPS+, .269/.338/.500, 44 XBH (14 HR), 51 RBI, 7 SB, 2.9 WAR

Abreu missed two weeks in June with an ankle injury and took some time to shake off the rust once he returned, but he has been a steady offensive contributor for the Red Sox for most of the year. The 25-year-old has also significantly outperformed Alex Verdugo, who he effectively replaced in right field after he was traded to the New York Yankees during the offseason.

12. RP Cade Smith, Cleveland Guardians

Stats: 62 G, 20 HLD, 2.00 ERA, 0.94 WHIP, 12.3 K/9, 63.0 IP, 2.0 WAR

11. RP Hunter Gaddis, Cleveland Guardians

Stats: 63 G, 27 HLD, 1.65 ERA, 0.77 WHIP, 8.3 K/9, 60.0 IP, 2.2 WAR

The Guardians have baseball's best bullpen with a 2.82 ERA that is more than a half run better than the Brewers (3.35) and Braves (3.36) who slot in behind them on that leaderboard. Closer Emmanuel Clase is having an amazing season, but the rookie tandem of Smith and Gaddis also deserves a ton of credit for the job they've done as the team's primary setup options.

Smith ranks sixth among qualified relievers with a 35.4 percent strikeout rate, while Gaddis leads all rookies and ranks seventh in the majors with 27 holds. They are also two of the 17 pitchers across baseball who have made at least 60 appearances in 2024.

Nos. 10-6

10. SS Tyler Fitzgerald, San Francisco Giants

Stats: 70 G, 155 OPS+, .292/.347/.557, 38 XBH (14 HR), 29 RBI, 16 SB, 2.7 WAR

Fitzgerald was an afterthought in the spring battle between veteran Nick Ahmed and prospect Marco Luciano for the shortstop job. Fast forward to August and Ahmed has been released, Luciano is in Triple-A and Fitzgerald is one of the most productive rookies in baseball. The 26-year-old only appeared among the Giants' Top 30 prospects once, checking in at No. 28 prior to the 2020 season, but he has emerged as a valuable young piece at a premium position.

9. SP Gavin Stone, Los Angeles Dodgers

Stats: 24 GS, 3.33 ERA (120 ERA+), 1.21 WHIP, 36 BB, 112 K, 135.1 IP, 2.3 WAR

Stone won the No. 5 starter job out of spring training and has been a stabilizing presence in a Dodgers rotation that has used 17 different starters on the year. The 25-year-old has tossed a team-high 135.1 innings and the Dodgers are 16-8 in his 24 starts. It will be interesting to see how he factors into the Dodgers playoff plans, assuming Tyler Glasnow and Yoshinobu Yamamoto both return before the start of the postseason.

8. 1B Michael Busch, Chicago Cubs

Stats: 125 G, 117 OPS+, .254/.340/.439, 42 XBH (16 HR), 50 RBI, 2.8 WAR

Busch crushed Triple-A pitching last season, but without a clear path to playing time on a stacked Dodgers roster he was deemed expendable and flipped to the Cubs in exchange for prospects Jackson Ferris and Zyhir Hope. The 26-year-old has been the Cubs starting first baseman from the jump this year, and with club control through the 2029 season, he should be a staple in the middle of the North Siders lineup.

7. OF Colton Cowser, Baltimore Orioles

Stats: 125 G, 121 OPS+, .247/.324/.446, 40 XBH (19 HR), 57 RBI, 8 SB, 2.5 WAR

It's been a roller-coaster season for Cowser, with the league adjusting to him after a blistering start, only for him to make the necessary adjustments on his end and return to a solid level of production:

• March/April: 86 PA, .303/.373/.632, 13 XBH (6 HR), 18 RBI
• May/June: 179 PA, .185/.279/.350, 13 XBH (6 HR), 16 RBI
• July/August: 186 PA, .280/.344/.452, 14 XBH (7 HR), 23 RBI

It's a rookie season that closely mirrors what James Outman did for the Los Angeles Dodgers in 2023.

6. OF Jackson Chourio, Milwaukee Brewers

Stats: 118 G, 108 OPS+, .272/.318/.444, 37 XBH (16 HR), 59 RBI, 19 SB, 3.0 WAR

Chourio is the youngest player to appear in an MLB game this season, clocking in roughly three months younger than Baltimore Orioles top prospect Jackson Holliday. The 20-year-old took his lumps early after breaking camp with a starting job, but he is hitting .312/.359/.520 with 15 doubles, 11 home runs, 43 RBI and 12 steals in 270 plate appearances since the beginning of June. With four more home runs and one more steal, he will become the first rookie in Brewers history with a 20/20 season.

5. SP Luis Gil, New York Yankees

Stats: 24 GS, 3.39 ERA (123 ERA+), 1.20 WHIP, 66 BB, 144 K, 124.2 IP, 2.8 WAR

Considering he was only on the Opening Day roster as an injury replacement for Gerrit Cole, it has been a wildly successful season for Luis Gil in the New York Yankees rotation.

The 26-year-old missed most of 2022 and all of 2023 recovering from Tommy John surgery, so the Yankees have understandably been carefully monitoring his workload, limiting him to fewer than 100 pitches in 22 of his 24 starts.

He is currently sidelined with a lower back strain, but it sounds like his stay on the injured list will just be for the minimum 15 days. The question then becomes whether he can secure a spot in the postseason rotation while also making a few final attempts to build his case for AL Rookie of the Year honors.

4. SS Masyn Winn, St. Louis Cardinals

Stats: 123 G, 108 OPS+, .284/.332/.423, 39 XBH (11 HR), 46 RBI, 10 SB, 4.6 WAR

Masyn Winn looked completely overmatched at the plate in his first taste of the big leagues last season, hitting .172 with a 28 OPS+ in 137 plate appearances after making his MLB debut on Aug. 18.

That was reason enough for the Cardinals to bring in veteran Brandon Crawford on a one-year deal as an insurance policy at shortstop if he continued to struggle, but he has taken the everyday job and run with it this year.

The 22-year-old has long been viewed as a potential Gold Glove defender, and he leads all shortstops with 13 Defensive Runs Saved while showcasing one of the strongest throwing arms in baseball.

Offensively, he has raised his OPS almost 300 points relative to his lackluster showing down the stretch in 2023, and it now looks like the Cardinals have their answer at shortstop for the foreseeable future.

3. SP Shōta Imanaga, Chicago Cubs

Stats: 24 GS, 3.08 ERA (134 ERA+), 1.06 WHIP, 22 BB, 140 K, 140.1 IP, 2.3 WAR

Left-hander Shōta Imanaga has made a smooth transition to Major League Baseball after eight seasons with the Yokohama Bay Stars in the Japanese League, and he has been a consistent bright spot for a Chicago Cubs team that has fallen short of expectations.

If not for two terrible starts during the first half of the season when he allowed a combined 19 hits and 17 earned runs across 7.1 total innings, his strong overall numbers would look even better.

With those two duds removed from the mix, he has a 2.10 ERA in 133 innings over his other 22 appearances, and his 14 quality starts slot in just ahead of Paul Skenes (13) to lead all rookie pitchers.

2. OF Jackson Merrill, San Diego Padres

Stats: 129 G, 126 OPS+, .292/.322/.490, 47 XBH (19 HR), 75 RBI, 14 SB, 3.6 WAR

With a .318/.348/.659 line that includes five doubles, three triples, six home runs and 21 RBI in 93 plate appearances in August, Jackson Merrill is making a compelling case to overtake Paul Skenes in the NL Rookie of the Year race.

For now, he stays at No. 2 in our rankings, but he's quickly approaching "1A" territory.

The 21-year-old has been a staple in the San Diego Padres lineup since breaking camp with the team and serving as the starting center field for the team's two games against the Los Angeles Dodgers in the Seoul Series to open the year.

It's a credit to his overall baseball acumen that he is learning how to play center field on the fly after spending the bulk of his time at shortstop in the minors, and he's still posting elite offensive numbers.

1. SP Paul Skenes, Pittsburgh Pirates

Stats: 17 GS, 2.16 ERA (192 ERA+), 0.94 WHIP, 25 BB, 130 K, 104.0 IP, 4.5 WAR

The gap between Paul Skenes and Jackson Merrill has narrowed considerably, but for now the Pittsburgh Pirates flame-throwing rookie still holds onto the top spot in our rookie rankings.

The Pirates have started to manage his workload by pitching him every six days, but he has continued to dominate when he takes the mound, tossing six scoreless innings of two-hit ball with nine strikeouts against the Cincinnati Reds on Aug. 22.

He has allowed more than two earned runs just twice in 17 starts, one of which was his MLB debut, and on top of his pristine 2.16 ERA he has also limited opposing hitters to a .198 average and .575 OPS across 400 plate appearances.

With a durable 6'6", 235-pound frame and an elite repertoire of pitchers, he should be a perennial Cy Young contender and the face of the franchise for a Pirates team on the rise in the coming years.