Matt Adams, 1B, Cardinals (Double-A Springfield)
A virtually unknown 23rd-round pick in 2009, Adams was the first player since 2000 to be selected out of Slippery Rock University, a school that has yet to have a drafted player reach the big leagues. He gained some attention with a .310/.355/.541 mark at Low-A Quad Cities last year in a season shortened by elbow problems, but as an older, bat-only prospect, he earned little true fanfare. Double-jumped to the Texas League for 2011, Adams keeps on raking, going 5-for-11 with three home runs over the weekend to lift his season mark to .322/.358/.643 in 29 games. At least 30 pounds more than his listed weight of 230 pounds—and that might be kind—Adams’ body will always be a concern, but he's continuing to prove that his bat deserves to be taken seriously.

Domonic Brown, OF, Phillies (Triple-A Lehigh Valley)
Brown's miserable showing this spring, in which he went 1-for-16 with nine strikeouts, ended early with a broken bone in his right hand, which at least made for much easier roster decisions. Now at Triple-A after warming up in the Florida State League, Brown has started his IronPigs stint with a six-game hitting streak, including a 4-for-9 weekend and two home runs. Forget about his big-league showing last year when he struggled in adjusting to a bench role, and forget about the miserable spring; he's still a monster prospect and will help the Phillies once they give him another shot.

Robbie Erlin, LHP, Rangers (High-A Myrtle Beach)
It was a week of no-hitters in the big leagues, and while Erlin hasn't quite thrown one, he has been the least hittable pitcher in the minors this year; after six starts, the Carolina League is batting a paltry .115 against him. On Friday, he went seven innings and gave up one hit. His last three starts have been even crazier: He has allowed just four hits over 21 innings (4-for-67) with one walk and 24 strikeouts. That's a 0.24 WHIP for you numbers folks. At the beginning of the year, he was one of the just-missed players from my Top 101 prospects, as he's just 5-foot-11 and has no more than average velocity. With each start giving more reassurance that he'll reach his ceiling as a good third starter, that lack of inclusion is looking more like a mistake.

Bryce Harper, OF, Nationals (Low-A Hagerstown)
I've been on a kick lately about questions concerning when a prospect will be in the big leagues, so I misinterpreted a tweet late last week asking about Harper. The questioner simply mentioned the word “promotion,” and I wrongly mocking him. All he meant was a promotion to the Carolina League, which is suddenly looking more like a possibility before the All-Star break. With three multi-hit games over the weekend, Harper's .371/.460/.701 season line is impressive enough, but his ridiculous .466/.544/.948 line in his last 16 games show that he's too good for this level, despite being just 18. Much like last year at junior college, Harper isn't just as good as advertised, he's accomplishing the nearly impossible by being better.

Hak-Ju Lee, SS, Rays (High-A Charlotte)
It's just 20 games, but everything about Lee's season seems so right; after an 8-for-14 weekend, the 20-year-old Korean is hitting .414/.469/.621 in his first 20 games as a Ray. Last year with Peoria, less than 20 percent of his hits went for extra bases, but with Lee's jump in average comes a jump in power. More than one-fourth of his hits have been non-singles, and he has already matched last year's total of four triples, while doubling his 2010 total with a pair of home runs. An average defender at short with a 60-65 arm, Lee is still prone to silly, out-of-control errors, but the projection of at least an average everyday shortstop (something there is not 30 of in the big leagues) is stronger than ever.

Carlos Martinez, RHP, Cardinals (Low-A Quad Cities)
Few players have been more hyped without pitching in the United States, but tales of Martinez's lightning arm spread quickly in a system that at times looks like Shelby Miller and everyone else. After beginning the year in extended spring training, Martinez arrived in Quad Cities on Saturday and let the hype train begin by firing four no-hit innings against Wisconsin while striking out six and walking one. But let's be patient in regards to projecting the 19-year-old. His fastball, which sat at 95-97 mph and touched 99 was as good as expected, if not better, but he remains a small right-hander who still needs significant development time in regards to his curveball and changeup. His ceiling is through the roof, but we need far more evidence before we plug Martinez at the top of a theoretical future Cardinals rotation.

Drew Pomeranz, LHP, Indians (High-A Kinston)
Six starts into his professional career, Pomeranz has had one so-so game and five excellent ones, including Saturday's, when he struck out eight over five shutout innings for his first professional win. With a 1.27 ERA and 42 strikeouts in 28 1/3 innings, Pomeranz has certainly been dominant, but no pitcher is perfect. While Pomeranz’s fastball and curveball are both true out pitches, his changeup lags behind and his control has occasional lapses. Pomeranz will likely move to Double-A for the second half of the season, just like 2009 first-round pick Alex White did last year, and should reach the big leagues in his second full season, just like Alex White did this year.

Eric Surkamp, LHP, Giants (Double-A Connecticut)
On the surface, Surkamp almost seems like a National League version of Erlin: He's left-handed, doesn't throw very hard, and yet he’s utterly dominant. On Saturday, he delivered his third consecutive double-digit strikeout game, and he leads the minors with 51 strikeouts in 32 2/3 innings, but scouts are still flummoxed as to exactly how he does it. It's not fair to call him a finesse arm—he has walked 15 batters this year—and he's also a backward pitcher who uses an above-average curve and changeup combination to set up his fastball as almost a chase pitch. All of his pitches play up due to a delivery than involves hiding the ball behind his head until nearly the moment of delivery. It's hard to say what Surkamp is right now other than very good statistically, and he'll likely get a chance to prove his game can work at Triple-A at some point in the second half of the season.

Mike Trout, OF, Angels (Double-A Arkansas)
When compiling this year's Top 101 prospect list, I flipped Trout and Harper's names numerous times, finally finishing with Harper at the top. A month into the season, it's still a coin flip, as Trout continues to run roughshod over the Texas League as a 19-year-old, going 3-for-10 over the weekend with a double, home run, and four walks to lift his season averages to .304/.398/.565 in 25 contests. With five home runs in 92 at-bats, Trout's power is developing rapidly, and his combination of excellent hitting skills, approach, and plus-plus speed and defense leave him as the most dynamic prospect in baseball. As for being the best over Harper? Keep flipping that coin.

Tim Wheeler, OF, Rockies (Double-A Tulsa)
The 32ndoverall pick in the 2009 draft, Wheeler's stock plummeted throughout the 2010 season, as he hit just .249/.341/.384 in his full-season debut. Those numbers looking even more mediocre when put into the context of the California League. Moved up to Double-A, because that's what you do with a first-round pick, Wheeler is have one of the biggest breakouts in the minors; after going 6-for-11 over the weekend with a pair of home runs, he's now hitting .318/.413/.682 in 28 games. On a tools level, Wheeler's greatest strength is a lack of weaknesses: He's a 50-55 runner who can hold his own in center field with a solid-average arm, while both his hitting skills and raw power fall into that solid-average range as well. Players with that combination of tools almost always make the big leagues, and most that do are everyday players, but few are stars.