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Major League Baseball's 2021 first-year player draft won't begin until Sunday, July 11, but a lot has happened on the amateur side since we presented our preseason top 50 in February. Now, more than two months later, we've decided to revise our top 10 based on renewed conversations with scouts and analysts as well as firsthand observations. 

Below, you'll find our top 10 players in this draft class. Do remember that our order is based on a combination of each player's potential and their expected draft slot. As an added bonus, we've included two additional writeups: one for the preseason top-50 player who has improved their stock the most, and another for the biggest faller.

As always, things are subject to change between now and the submission of the Pirates' pick.

1. Jack Leiter, RHP, Vanderbilt 

Preseason: No. 1

With a little over two months to go, Leiter is positioned to lead the class from flag to flag. Yes sir, his fastball can boogie, especially up in the zone thanks to his ability to impart spin and create a flat plane. Scouts would like to see more consistency from his secondaries, including both of his breaking balls, but he's a good athlete and a hard worker who should be able to make the necessary refinements. Some teams with high picks aren't even discussing Leiter as a contingency option, suggesting the industry believes he'll go No. 1 barring an injury or a Bob Nutting-forced cheap out.

2. Jordan Lawlar, SS, Dallas Jesuit HS (TX)

Preseason: No. 2

If Leiter doesn't go first overall, then Lawlar would be the logical alternative. He's drawn comparisons to Royals prospect Bobby Witt Jr. because of his advanced age (he'll celebrate his 19th birthday before the draft), his Texas residency, and his skill set. His biggest fans within the industry believe he'll stick at shortstop for the long haul and have above-average grades for every tool at maturation, making him a potential all-star. Teams expect he'll require a larger signing bonus to forgo his commitment to Vanderbilt than the $5.2 million received by last year's No. 2 pick Heston Kjerstad.

3. Marcelo Mayer, Eastlake HS (CA)

Preseason: No. 5

Mayer doesn't receive as much attention as Lawlar does, but he's another high-end prep shortstop. Unlike Lawlar, there's no question that Mayer is going to remain at the six. He has all the proper weaponry, including a strong and accurate arm and light feet. Mayer's offensive future presents more volatility. There are those in the game who believe he'll grow into 15-to-20-homer power from the left side. Should that come to fruition, he's going to make whichever team lands him a happy one.

4. Kumar Rocker, RHP, Vanderbilt

Preseason: No. 4

Rocker remains the most famous player in this class, which in turn has led to some overexposure that borders on fatigue. He's had a tremendous collegiate career and his slider is one of the best chase pitches in the class, yet teams have reservations about his fastball's results (improved this season), his mechanics, and his durability. He recently went through a stretch where his velocity was down about two ticks from normal, according to data obtained by CBS Sports. Rocker's velocity has since rebounded, but that fluctuation isn't going to help his case with those who doubt him. He's hanging steady at No. 4, even though it's possible he slips a little further come draft day.

5. Henry Davis, C, Louisville 

Preseason: No. 8

To quote a snippet from our preseason rankings: "Don't sleep on Davis as a dark horse to go in the top five." Now he's in the top five, having further established himself as a good prospect by flirting with a .400 average and a 2-to-1 walk-to-strikeout rate so far this season. Davis seldom whiffs, he hits the ball hard, and he's going to remain behind the plate (with a strong arm to boot). There were scouts who were concerned that his swing was too strength-based to work against top-notch velocity. Maybe that proves to be the case, but some team is going to jump at the opportunity to find out.

6. Sal Frelick, OF, Boston College

Preseason: No. 16

The go-to comparison with Frelick is to Yankees outfielder Brett Gardner. (We referenced Sam Fuld, a Diet Gardner, in our preseason capsule.) It works on a few levels, as Frelick is a well-rounded player with an all-out mentality who makes the most of a small frame (he's listed at 5-foot-9). Indeed, his height might be the biggest knock against him, though it's unclear if that criticism holds water. The Diamondbacks, for example, have done well plucking Corbin Carroll and Alek Thomas in recent drafts; their decision makers were also involved in taking Mookie Betts and Andrew Benintendi during their days in Boston. Arizona picks sixth, so we're putting Frelick at No. 6, even if there's no guarantee the Diamondbacks will go back to the short outfielder well.

7. Gunnar Hoglund, RHP, Ole Miss

Preseason: No. 20

Here's the best statistic to demonstrate Hoglund's above-average control: he's walked 2.6 batters per nine innings this season, and that's by far the worst mark of his collegiate career. In addition to being a polished strike thrower, he has a broad arsenal that features a ton of spin, beginning with his boring fastball and extending to his cutter-like slider. Add in how Hoglund has been vetted by the Southeastern Conference, and he should work his way into the top 10 as a quick-moving No. 3 or 4 starter. 

8. Kahlil Watson, SS, Wake Forest HS (NC)

Preseason: No. 7

The big question about Watson pertains to his position. Some evaluators think he can stick at short, or elsewhere on the dirt, while others envision him as an outfielder with a plus arm. Wherever he lands defensively, he's going to make his money at the plate. Watson has a beautiful, torque-heavy swing that's ripped from Hitting Twitter and that should result in above-average power. He's going to have to work on his approach, but that's true of most every teenage prospect -- and few of them have his upside.

9. Adrian Del Castillo, C, Miami

Preseason: No. 6

Positional questions also haunt Del Castillo, who may have to settle for playing first base or hitting on a designated basis by the time he reaches the Show if he can't find a way to improve his receiving and shorten his arm stroke. Usually, that kind of defensive profile would result in a worse ranking, but Del Castillo has a few things working in his favor. For one, it's likely that he's going to benefit from rule changes concerning robot umpires and the universal DH in the next Collective Bargaining Agreement. For another, he's an intelligent hitter with good strike-zone management and bat-to-ball skills. He has above-average strength, too, though he's a hitter with power rather than a power hitter.

10. Colton Cowser, OF, Sam Houston State

Preseason: No. 12

Cowser has been on scouting radars since joining Team USA as one of its youngest members. He's solidified his standing this season, recording more walks than strikeouts while hitting 12 of his 20 career home runs in his first 35 games. Cowser's hitability and combination of power and speed should allow him to become the highest selected Bearkat in school history, dethroning Glenn Wilson (18th in 1980).

Into the great wide open: Sam Bachman, RHP, Miami (OH)

Bachman, who entered the spring ranked 41st, is a draft-room debate about long- versus short-term value waiting to happen. He has big-time stuff, including a fastball that has eclipsed 100 mph and a swing-and-miss slider, and he's struck out more than 40 percent of the batters he's faced this year. He isn't in the top 10 because teams have reservations about his durability, a concern that stems in part from his past arm issues and in part from his unusual arm action. These sorts of things seldom happen for as often as they're discussed, but it's theoretically possible that whichever club pops Bachman will entertain hotshotting him to the big-league bullpen, à la Garrett Crochet.

Freefalling: Jud Fabian, OF, Florida

One of the surefire ways to lose standing with scouting departments is to strike out at Galloian levels. Fabian has had an atrocious spring in that regard. He's punched out in nearly a third of his plate appearances, a rate that obscured his 12 home runs and his .902 OPS. Fabian was our preseason No. 3 based on his plus power potential and his Southeastern Conference vetting; now, he'll have to settle for going sometime later, albeit still in the top three rounds.