The 2019 MLB trade deadline is going to be a leaguewide learning experience.

With the removal of the August waiver-trade period, teams will have to commit to being buyers or sellers by July 31 rather than waiting around an extra month to get a better feel for how things are playing out.

Look no further than the 2017 Houston Astros and their trade for Justin Verlander to see what kind of impact an August waiver trade could have on the postseason picture.

With teams forced to choose a direction one month earlier, there figures to be far more activity at this year's non-waiver trade deadline on July 31 than in years past. 

While we're still more than two months away from that flurry of excitement, it's never too early to look ahead at who some of the top trade targets will be this summer.

Here, we've highlighted seven impact players to watch, while also providing a quick rundown of the always active relief pitching market.

The Top Relievers

RHP Alex Colome, Chicago White Sox

Colome has converted all seven of his save chances with a 2.25 ERA, 0.75 WHIP and a .132 opponents' batting average. His team control through the 2020 season and late-inning experience should make him an attractive target, and the White Sox have shown a willingness to deal bullpen arms in recent years.

RHP Ken Giles, Toronto Blue Jays

Giles has been overpowering closing games for a non-contender in Toronto. He's nailed down nine of 10 save chances with a 1.56 ERA, 1.04 WHIP and a 26-to-5 strikeout-to-walk ratio in 17.1 innings. He too has team control through the 2020 season, so he's more than just a rental.

RHP Mychal Givens, Baltimore Orioles

Another solid late-inning arm closing games for a non-contender. Givens has used his power stuff to save four games in five chances, posting a 2.89 ERA and 24 strikeouts in 18.2 innings. He won't reach free agency until after the 2021 season, so the O's don't need to trade him unless they get an offer they can't refuse.

RHP Shane Greene, Detroit Tigers

The Tigers pitching staff has been a pleasant surprise this season, and Greene has been a big part of that with an AL-leading 15 saves in 15 chances to go along with a 1.50 ERA, 0.78 WHIP and a .154 opponents' average. It will take a lot to pry him loose, but the Tigers might be best served selling high.

LHP Will Smith, San Francisco Giants

Smith might be the best rental reliever on the market, and pitching for a non-contender in San Francisco, he's all but certain to be moved. Lefties are always in demand at the deadline, and while there's no guarantee he'd close for a contender, he's been excellent in that role with 10 saves in 10 chances and a pristine 0.89 WHIP and .185 opponents' average.

Other Notable Relievers Who Could Move

• LHP Jake Diekman, Kansas City Royals
• RHP David Hernandez, Cincinnati Reds
• RHP Shawn Kelley, Texas Rangers
• RHP Ian Kennedy, Kansas City Royals

RF Nicholas Castellanos, Detroit Tigers

The Detroit Tigers listened to offers for slugger Nicholas Castellanos leading up to the trade deadline last year and all offseason. However, they have yet to find a good enough return to pull the trigger on moving their best hitter.

With Castellanos heading into free agency this coming offseason, the Tigers may have to take the best offer on the table at the trade deadline.

The 27-year-old is a homegrown star whom the Tigers took with the No. 44 pick in the 2010 draft. He proceeded to climb the ranks of the Detroit farm system as the team's top prospect. That undoubtedly contributes to the Tigers' hesitance when it comes to dealing him.

There's also the matter of his below-average defense in right field watering down his overall value. The metrics were not kind to him last year (-19 DRS, -12.3 UZR/150), and this season has not been much different (0 DRS, -11.0 UZR/150). He's probably best suited as a DH, despite his age.

Still, Castellanos is a right-handed power bat in the prime of his career. He hit .298/.354/.500 with 46 doubles and 23 home runs last season, and he has a 112 OPS+ with 12 doubles, three triples and three home runs so far this year.

It might take a few mid-level prospects with upside to acquire him, but he can give a contender's offense a major boost in the second half.

SP Mike Minor, Texas Rangers

The Texas Rangers took a chance signing Mike Minor to a three-year, $28 million deal and moving him back into a starting role after a successful season out of the bullpen for the Kansas City Royals in 2017. He had missed the previous two seasons recovering from a torn labrum in his left shoulder.

Minor ended up being the Rangers' most reliable starter in 2018, posting a 4.18 ERA, 1.12 WHIP and 132 strikeouts in a team-high 157 innings.

Now he's in the midst of the best season of his career.

The 31-year-old has recorded five quality starts in eight appearances, including a three-hit shutout against the Los Angeles Angels back on April 16. He ranks among the AL leaders in ERA (2.68, seventh), WHIP (1.04, 10th), innings pitched (53.2, fifth) and opponents' batting average (.207, tied for ninth).

Between his strong performance this season and his team-friendly $9.8 million salary in 2020, he's an attractive trade chip.

He won't come cheap, but he could make a real difference this season and next.

1B Jose Abreu, Chicago White Sox

How much do the Chicago White Sox value Jose Abreu as a veteran leader in a young clubhouse?

That's the question they need to answer this summer with the 32-year-old slugger set to enter free agency for the first time following this season.

After suffering through a down year in 2018 during which he posted career-lows in batting average (.265), OPS (.798), OPS+ (117), home runs (22), RBI (78) and WAR (1.7), he has looked better in the early portion of this season.

Abreu is hitting .269/.331/.513 for a 126 OPS+ with 11 doubles, nine home runs and 35 RBI, which has translated into 0.9 WAR. That puts him on pace to more than double his 2018 mark.

The peripherals are also promising, as he's had a sharp downturn in his soft-contact rate (17.2 to 13.2 percent) and a nice uptick in his walk rate (6.7 to 8.1 percent).

Abreu's lack of defensive value and status as a rental will limit his trade value. Still, the White Sox should be able to add a few quality prospects to their farm system if they pull the trigger on moving him this summer.

SP Zack Wheeler, New York Mets

On the surface, Zack Wheeler has taken a significant step backward after his brilliant run in the second half last season.

After posting a respectable 4.44 ERA during the first half last season, Wheeler was virtually untouchable after the All-Star break, logging a 1.68 ERA, 0.81 WHIP and a .179 opponents' batting average in 11 starts.

So far in 2019, he has a 4.35 ERA and 1.35 WHIP over 49.2 innings.

However, below the surface, he has a 2.71 FIP with a career-high 10.5 K/9 while showing a nice increase in his groundball rate (44.2 to 51.1 percent). A fairly unlucky .336 BABIP is at least partially to blame for his early mediocrity.

He has posted five quality starts in his last six appearances after a rocky first two outings, with a 2.93 ERA during that span, including back-to-back 10-plus strikeout games.

Even as a rental, Wheeler figures to command a significant return. However, all bets are off if the New York Mets are still in contention in July.

SP Madison Bumgarner, San Francisco Giants

It's hard to imagine Madison Bumgarner wearing anything other than a San Francisco Giants jersey. But as the homegrown ace navigates the final year of his contract for a team that is rapidly slipping out of contention in the NL West, it's a real possibility.

The 29-year-old has a limited no-trade clause, according to Ken Rosenthal of The Athletic, with the ability to veto trades to the Atlanta Braves, Boston Red Sox, Chicago Cubs, Houston Astros, Milwaukee Brewers, New York Yankees, Philadelphia Phillies and St. Louis Cardinals.

At first glance, it might seem odd that he loaded up his no-trade list with contending teams. But as Rosenthal noted, Bumgarner "should be motivated to approve a trade" since any impending free agent who gets traded in the middle of the season is ineligible for a qualifying offer and won't have draft-pick compensation tied to his free agency.

This list gives Bumgarner more control of which contender he ultimately winds up with at the deadline.

Is it a foregone conclusion that he'll be playing elsewhere in August? While it should be, you never know when it comes to homegrown fan favorites.

New team president Farhan Zaidi might not be willing to take the public relations hit unless he gets a big enough return that he can sell the move to the fanbase.

If Bumgarner keeps racking up quality starts while looking more and more like the pitcher he was before a pair of injury-plagued seasons, that big return could be within reach.

3B Anthony Rendon, Washington Nationals

The Washington Nationals opted against trading Bryce Harper at the deadline last season, despite a 53-53 record on July 31 that left them 5.5 games back in the NL East and five back for the No. 2 wild-card spot.

They are already eight games under .500 this season and are staring at a 7.5-game deficit in the division standings, and the NL East has gotten much tougher in the past year.

How will all of that impact their handling of free-agent-to-be Anthony Rendon?

While the Nationals have had an ongoing dialogue with their star third baseman on a potential extension, Jon Heyman of MLB Network reported on April 18 that there's "believed to be a decent-sized gap" in negotiations and that "optimism isn't necessarily there yet" on a deal getting done.

The 28-year-old got off to a red-hot start this season, hitting .371/.451/.771 with 10 doubles, six home runs and 18 RBI in his first 19 games. However, he missed 14 games after taking a 95 mph fastball off his left elbow on April 20, and he's hitting only .120/.214/.200 in 28 plate appearances since his return to action.

Assuming he puts the elbow issue behind him and returns to form, he could be this year's Manny Machado in terms of value at the trade deadline.

Rendon posted a 138 OPS+ while averaging 42 doubles, 24 home runs and 5.0 WAR over the past two seasons, and he was on a roll this year before he got plunked.

The Nationals were unwilling to wave the white flag until August last year, but they won't have that luxury this time around with the elimination of the waiver-trade window. Expect to see Rendon on the block unless they improve in a hurry.

SP Trevor Bauer, Cleveland Indians

One of the biggest storylines from this past offseason was the Cleveland Indians' willingness to listen to offers for standout starters Corey Kluber and Trevor Bauer.

While both pitchers ended up staying put, Bauer didn't mince words in an interview with Ben Reiter of Sports Illustrated in February, which contained the following tidbit: 

"Even though he won't reach free agency until after the 2020 season, [Bauer] says, 'I won't be with the Indians next year,' meaning after 2019. He is certain that the cash-strapped franchise will trade him for prospects by next winter. He's fine with it. It's logical."

The 28-year-old is earning $13 million this season, and that could approach $20 million next season in his final year of arbitration. The Indians spent a good portion of this past offseason looking for ways to trim the payroll, so he has a point.

After posting a 2.21 ERA, 1.09 WHIP and 221 strikeouts in 175.1 innings last season to finish sixth in AL Cy Young voting last year, he's off to a solid start again this season with a 3.02 ERA and 1.11 WHIP over an MLB-leading 59.2 innings.

The Indians will be asking for a king's ransom, but there will not be a better way to spend top-tier prospect capital at this year's trade deadline than on the Cleveland standout.

All stats courtesy of Baseball Reference and FanGraphs, unless otherwise noted.