Here's a look at some players to keep a watch on, because you may see them in a Major League ballpark in the near future.
On the mound
Three pitchers still in the Top 10 could be heard from before long.
Julio Teheran, currently the No. 3 overall prospect, is No. 1 on the Braves' Top 20. The 21-year-old right-hander was up and down during his big league debut last year, but that hasn't carried over to this season, which he has spent in Triple-A. He's been particularly good of late, holding opponents to two earned runs over 16 May innings (1.13 ERA). International League hitters have just a .214 average against him in three outings this month and he's walked just two while striking out 14. With Mike Minor sporting a 6.59 ERA, Teheran could get another shot soon.
No. 4 overall prospect Shelby Miller hasn't had the success Teheran has experienced thus far this season. He has been better of late, with a 3.18 ERA in two May starts. His overall stuff is still fine, but he's been a little too up in the zone, causing him to be much more hittable despite an 11.3 K/9 ratio. There isn't really any room in the Cardinals' rotation, but perhaps a Lance Lynn-type role, by which he could step in to fill a rotation spot late in the year, could get Miller his first taste in St. Louis.
Jacob Turner (No. 13 overall) is another pitching prospect in Triple-A who is working his way back to getting another big league look. He was in the mix for a rotation spot this spring, didn't win it, then landed on the disabled list. After four starts in the Florida State League, he's back in Triple-A Toledo and had a solid first outing. With Max Scherzer and Rick Porcello scuffling with Detroit, Turner could receive an opportunity to help out.
There are two 2011 first-round picks in Double-A to definitely keep an eye on. That might sound premature, but both Trevor Bauer (No. 8 overall) and Danny Hultzen (No. 14) were thought to be fast-trackers when they were taken by Arizona and Seattle, respectively. Both have been tough to hit, with Bauer posting a .192 BAA and Hultzen an even stingier .134. Both have had some issues with walks, but with the two big league teams not faring all that well, could they bring their prized draftees up for some assistance soon?
At the plate
The hitters' pool is not as rich. There clearly isn't a Harper or Trout waiting in the wings right now. At the Triple-A level, there are three hitters who stand out as potential impact call-ups. None has been hitting better than the Cubs' Anthony Rizzo (No. 33 overall), who has a 1.078 OPS with Iowa. There's no question about his ability to hit Triple-A pitching, but he needs another opportunity in the big leagues. However, Bryan LaHair has been hitting for Chicago, so there's no room at first base. LaHair has played a good amount of outfield, though ... food for thought.
The Pirates could use some offensive help, but is Starling Marte (No. 36) the answer? More important, is he ready? He's hitting .261 with a .760 OPS in Triple-A. He still needs to improve his plate discipline and he's been struggling recently. If he can get hot, though, seeing him in left field at PNC Park might be a welcomed sight.
The Blue Jays have a young catcher in the big leagues in J.P. Arencibia. But as a bat-first backstop who is hitting just .222 and slugging only .364, could they give Travis d'Arnaud (No. 21) a shot? Like Marte, he hasn't been hitting that well recently, but many see him as a better all-around backstop than Arencibia in the long run.
As with the pitchers, there are a couple of hitters at the Double-A level who could work their way up two levels before the year is out. A year ago, the Royals' Wil Myers (No. 17) was on the fast track, but then he had a rough season while dealing with nagging injuries. A strong Arizona Fall League has led to an outstanding return engagement in the Texas League, where he has a 1.165 OPS. Room could be made in right field with Jeff Francoeur giving way. He's also been playing a little third base, making things a little more interesting. Perhaps Mike Moustakas moves to first to spell the struggling Eric Hosmer?.
Finally, there's third baseman Nolan Arenado of the Rockies. He got a nice long look during Spring Training, but given that he hadn't played above Class A, it was a bit premature to think he could make such a big jump. He's hit capably during his first taste of Double-A, though the power hasn't really been there (.423 SLG). Working in his favor is the lack of any Major Leaguer blocking his path, so stay tuned.