Minor League Heat Check: Which prospects are making noise and which are making outs?

Dean Treanor and Jim Riggleman were talking about the perils of managing in Triple-A, how guys move in and out on a whim, when they got around to the hottest hitter in the minor leagues. Treanor manages him. Riggleman was tired of facing him.

"I'd like to see this guy move," Riggleman said.

All across Triple-A, opposing managers are uttering similar sentiments about Gregory Polanco, the 22-year-old who soon enough will join Andrew McCutchen and Starling Marte to give the Pittsburgh Pirates a five-tool Voltron of an outfield.

Just how soon is the question. By keeping him in the minor leagues this long, the Pirates don't have to worry about losing him as free agent until after the 2020 season. Holding off on his promotion to stave off an extra year of arbitration, on the other hand, would mean keeping him in the minor leagues at least another month, something that gets more unpalatable by the day with his .400/.457/.632 slash line and the Jose Tabata-Travis Snider platoon in right field proving feckless.

[Also: Top prospect Archie Bradley goes on DL with 'mild' elbow strain ]

"Would I like to have him here longer to develop a little more? Yeah," Treanor said. "But then on the other side of that, if they feel they need him there, I'm not going to say, ‘No, he's not ready.' "

Treanor and Pirates manager Clint Hurdle talk at least once a week, sometimes more, and the reports on Polanco remain the same: incredible talent, crazy bat speed from the left side, freakish athletic ability at 6-foot-4, 220 pounds … and still room for improvement. With McCutchen locked into center field, Polanco has needed to learn right field. Daily drills include fielding balls hit over his head and into corners, and learning the nuances of tracking balls hit to right instead of center.

Polanco's baserunning is a point of emphasis, too, as the Pirates want to take advantage of his well-above-average speed. Reading pitchers and stretching his leads – "This guy takes about three strides to get to second," Treanor said – can add to the danger he poses.

"Just the difference in less than a month is dramatic," Treanor said. "I don't want to lose him. But ..."

But he knows. Polanco is a big leaguer, and chances are he won't be around for the next end-of-the-month Minor League Heat Check at Yahoo Sports. Meanwhile, here are 20 other prospects, in no particular order, who have seen Aprils good and bad.

Mookie Betts, 2B, Boston (Double-A): If anyone stands to challenge Polanco for best minor leaguer in April, it's Betts, the fifth-round draft pick from 2011 who jolted onto the scene last season and has more than solidified his prospect status this year. Between his height (5-foot-9) and power (14 extra-base hits already), Betts shares some commonalities with the man blocking him, Dustin Pedroia. He's just one of a plethora of top-end Red Sox prospects, with two more potential big league infielders (third baseman Garin Cecchini and shortstop Deven Marrero) thriving likewise in the high minors.

Joey Gallo, 3B, Texas (High-A): Nobody in the minor leagues possesses the power of Gallo, a sandwich-round pick in 2012. During high school in Las Vegas, stories of his tape-measure shots would be compared to those of another slugger: Bryce Harper. Among his nine home runs, 20 walks and 28 strikeouts in 106 plate appearances, Gallo is the heir to Adam Dunn as King of the Three True Outcomes.

Ben Lively, SP, Cincinnati (High-A): Aptly named, the right-hander in his first full season has the single best statistical flourish in the minor leagues thus far this season: 40 strikeouts, one walk. His 13 hits allowed and one earned run over 29 innings aren't bad, either. He should join top Reds prospect Robert Stephenson in Double-A any day now, forming the minor leagues' best one-two rotation punch.

Kris Bryant, 3B, Chicago Cubs (Double-A): Pretty much doing what's expected. A .298/.427/.571 line in his first full season after going second overall in the 2013 draft. He's going to be on the North Side soon enough, and when he arrives, he'll be a star immediately.

Javier Baez, SS, Chicago Cubs (Triple-A): Only 10 hits in 63 at-bats, and the sort of trouble at shortstop that leads most to believe he'll end up at second or third base, are not the sort of start he wanted. One scout's assessment on Baez: "This is good for him. Guys at Triple-A are crafty. He needs to get used to that, because he's going to see a lot of breaking balls when he comes up."

Oscar Taveras, OF, St. Louis (Triple-A): Healthy and hitting. With Peter Bourjos' struggles and Jon Jay being Jon Jay, it's just a matter of time before Taveras is playing every day. The only question is whether he is a center fielder long-term. He has played three of 20 games there this season, and scouts' consensus is: No. For now, though, his glove is adequate enough to sandwich him between Matt Holliday and Allen Craig, even if such a defensive alignment would be mighty porous.

Jesse Winker, OF, Cincinnati (High-A): Gorgeous, pure left-handed swing. One scout threw a Christian Yelich comp on him. Winker hit as a rookie sandwich pick in 2012, hit in Low-A last year and has raked thus far in the Cal League. Could see Double-A before his 21st birthday in August and the major leagues by that time next year.

Raul Mondesi, SS, Kansas City (High-A): Yes, he's Raul Mondesi's kid. And, yes, he could be better than pops, who spent more than a dozen years in the big leagues and hit 271 home runs. Mondesi 2.0 is a superior athlete, with a legit shortstop glove and burgeoning speed to boost, and at 18, he's just three steps from the major leagues.

Gabriel Guerrero, OF, Seattle Mariners (High-A): Yes, he's Vladimir Guerrero's nephew. And, no, he probably won't be better than unc, who is a first-ballot Hall of Famer. But he may well be better than Tio Wilton. The power is there. The key is to avoid the Guerrero curse: Gabriel hasn't met a pitch he won't swing at, and 27 strikeouts in 98 at-bats is worth monitoring.

Aaron Judge, OF, New York Yankees (Low-A): Already 22, the first-round pick from last season should be in a more challenging league. One concern: His .333 batting average is awfully hollow, with just four extra-base hits, for a 6-foot-7, 230-pounder. The power is there. He needs to tap into it so the world can hear John Sterling bust out a "Judge Dredd" home run call.

Dalton Pompey, OF, Toronto (High-A): Helium alert. The 21-year-old Canadian is crushing Florida State League pitching at a .366/.433/.495 clip, his bat finally catching up to a center-field glove and set of wheels that distinguish him further. With Colby Rasmus an impending free agent, Pompey is looking like the Blue Jays' center fielder come 2016. And that talent, at that position, in a switch hitter – he's stronger from the left side but plans on staying switch – screams potential star.

Jon Singleton, 1B, Houston (Triple-A): The off-field maladies that have hindered Singleton's development have slowed for now, and he's the rare first-base prospect who actually warrants prospect status. He's got nine home runs and a slugging percentage near .700, and he'll be an instantaneous upgrade over the Jesus Guzman/Marc Krauss/Chris Carter pu pu platter the Astros are serving these days.

Bubba Starling, OF, Kansas City (High-A): It's getting close to the point where the bust label can be affixed to Starling. He turns 22 in August and is stuck in Class A, where he's hitting .127/.263/.228. He can catch the ball in center, and he's still a remarkable athlete, but scouts who see him wonder the same thing: How much longer until he pulls a Drew Henson or Chris Weinke and heads to college as a quarterback?

Joc Pederson, OF, Los Angeles Dodgers (Triple-A): He doesn't fit anywhere in the Dodgers' $429 million outfield, which is a shame considering none of the four they have now is anywhere near as good in center field as Pederson. So he'll bide his time at Triple-A either as the best trade bait in the game or wait for an injury that will allow him to bring his .389/.495/.644 line to the big leagues.

Ryan McMahon, 3B, Colorado (Low-A): The Rockies have a sneaky strong farm system with a plethora of high-upside everyday players: outfielder David Dahl, infielders Trevor Story and Rosell Herrera, and McMahon, a second-round pick last season who has 20 home runs in 291 minor league at-bats. He's an athlete, too. McMahon quarterbacked Mater Dei High in California, former stomping grounds of Matt Barkley and Matt Leinart.

Julio Urias, SP, Los Angeles Dodgers (High-A): At 17 years old, Urias is by far the youngest player in his league, and the Dodgers are treating him accordingly: short outings, limited pitch counts, safety, safety, safety. After throwing four scoreless innings in his first start, he struggled in his next three appearances. The stuff remains there, though, and there's little reason yet to be concerned for a left-hander who wouldn't be out of high school in the United States and last season dominated a full-season league.

Cam Bedrosian, RP, Los Angeles Angels (Double-A): Legitimate question: What's the cooler thing about Cam Bedrosian? That he has struck out 26 hitters in 10 2/3 innings between High-A and Double-A, or that his given name is Cameron Rock Bedrosian? The latter, of course, seeing as his father, Cy Young-winning reliever Steve Bedrosian, was nicknamed Bedrock. Still, 26 strikeouts among 32 outs is pretty incredible, and Bedrosian, 22, could be up to fortify the Angels' bullpen soon.

Alex Meyer, SP, Minnesota (Triple-A): The key component in the Denard Span deal added a changeup this offseason, and seeing as his 6-foot-9 frame gave him a distinct enough advantage already with a high-90s fastball, the new wrinkle gives the Twins even more hope he can be the sort of power starter they so desperately need to complement their array of free-agent signings.

Brandon Nimmo, OF, New York Mets (High-A): The Mets took Nimmo with the 13th pick in the 2011 draft, betting on his massive talent that needed more polish than a pair of bluchers worn for a road race. New York has moved him slowly, and in his third full season he's beginning to resemble what they hoped would develop. Still just 21, Nimmo is hitting .407/.530/.549 in the FSL and could force the Mets to abandon their level-by-level tack with him.

Byron Buxton, OF, Minnesota (High-A): The best player in the minor leagues still hasn't taken an at-bat this year, his left wrist injured in a diving catch during spring training. He'll soon join Fort Myers, where he ended last season, but could move up to Double-A in a hurry. If all goes well there, the possibility of a September cameo, though unlikely, exists. And in the meantime, the Heat Check gets to check in every month and appreciate the sort of talent that will star in the big leagues for years to come.

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