Javier Baez, SS, Cubs (High-A Daytona)
Of all the prospects in the minors, Baez’s status might have the most volatility, with the skill set to blossom into a superstar and the deficiencies that could terminate the dream before it begins. With elite bat speed and the type of raw power that can find a home in the middle of any major-league lineup, Baez could end up as the top prospect in the game. But his one-speed-fits-all approach on both sides of the ball can be limiting: His aggressive, see-ball-hit-ball mentality at the plate often puts him behind in counts and vulnerable to offerings out of the zone, and his tendency to rush the actions and the throws makes him error prone despite his exquisite hands at shortstop. Baez is warming up and is a good candidate to explode this summer, with a chance to sneak into the top 10 prospects in the game. But the Double-A test is looming on the horizon, and without more nuance to his game and a more refined approach, Baez could take a big step back against better competition. The talent is extreme. The risk is just as extreme. —Jason Parks
Sonny Gray, RHP, Athletics (Triple-A Sacramento)
This year has seen Gray return to form from his days as one of the top arms in the country at Vanderbilt. He’s improved his pacing through his motion, and has seen a sharp improvement in the command of each of his offerings, which took a step backward in 2012. His best weapon has been his big, hard 12-to-6 curve, which plays as a plus-or-better offering that he can drop in the zone or bury. It’s the very definition of a swing-and-miss pitch, and PCL hitters have had difficulty picking it up out of his hand. His off-speed offering is an average, straight change and he’ll mix in a quality slider on occasion that flashes above average. The fastball, while lacking great plane, is explosive, and he can dial it up as high as 97 mph. Gray works the bottom shelf without mercy, elevating later in counts and wielding his curve as a put-away hammer. At this point, there is very little left for him to work on at the minor-league level, and A’s fans should look forward to seeing him in Oakland in the not-too-distant future. He’s a potential front-end arm and could realize that potential quickly upon arrival. —Nick Faleris
Eddie Butler, RHP, Rockies (High-A Modesto)
The last time we checked in on Butler, he was tearing through the Low-A South Atlantic League with his power fastball-slider combination, leading a scout source to predict that he would finish this season in Double-A. After posting a 1.69 ERA and yielding just 25 hits in 54 1/3 Low-A innings, the 22-year-old righty recently made a step in that direction by earning a promotion to High-A Modesto.
A supplemental first-round pick in last year’s draft, Butler is quickly becoming one of the Rockies’ top prospects. While his results through two High-A starts have been unspectacular––seven runs allowed in 11 innings––the stuff has remained dominant. In his California League debut, a scout source said Butler showed a 92-96 mph fastball (T97) with plus-plus life. He also mixed in a mature slider and sinking upper-80s changeup, both of which could become 60-grade offerings. Wiry strong at 6-foot-2, 180 pounds, Butler projects for average control and command, but isn’t there just yet; he has walked 32 in 65 1/3 frames. If the secondaries and command develop, Butler could become a ground-ball machine with bat-missing stuff; a potential number-two or -three starter at the major-league level. —Jason Cole
Mike Foltynewicz, RHP, Astros (Double-A Corpus Christi)
Foltynewicz might be the most underrated arm in the minors, or, as one scout put it, “He just might have the best raw stuff of any arm in the minors.” That’s high praise given the field of contemporaries, but it’s a case that can be made, especially when looking at the raw power of the fastball. The 21-year-old righty routinely works the heater in the 96-98 range, and has touched over 100 mph in the majority (if not all) of his appearances this season. The breaking ball gets mixed reviews, with some seeing a plus pitch in the future while others aren’t quite as aroused by its potential, and the changeup is currently below average with a chance to be average. But the fastball is an 8 on the 2-8 scale and a true carrying weapon. If you take an optimistic view, Foltynewicz could end up with an elite pitch, a plus breaking ball, and a usable changeup, with a big, strong durable frame capable of holding innings and velocity, and enough feel to make it all work. That’s a hell of a profile. That’s an impact starter. The more pessimistic crowd loves the fastball but is tepid on the secondary stuff, putting his ultimate ceiling in the middle-to-back of a major-league rotation and not at the front of it. Baseball Prospectus’ own Jason Cole will be sitting in on a Corpus Christi series very soon, so a full scouting report (with video) on Foltynewicz will be on the menu. —Jason Parks
Johnny Hellweg, RHP, Brewers (Triple-A Nashville)
The lone member of my radar gun’s 100-mph club this year, Hellweg produces seemingly effortless elite velocity out of his 6-foot-9 frame, sitting mid-90s with heavy late life and routinely touching higher. Although it’s a borderline 80-grade offering, it plays down at present because of his control issues; he has walked 39 and struck out 43 in 56 2/3 Triple-A innings.
While Hellweg’s long levers help him create extension in front of the rubber, they also make his mechanics more difficult to repeat. When I saw him last month, he tossed three dominant innings but was unable to adjust in the fourth when his arm began to drag. That led to four walks in a five-hitter span, and he was quickly chased from the game.
With a potential solid-average power curve and average changeup––though both are presently inconsistent––Hellweg may be relegated to the bullpen if his command doesn’t progress. The 24-year-old prospect has made strides of late, however, as he walked only two in seven strong innings on May 31. —Jason Cole
Ian Krol, LHP, Nationals (Double-A Harrisburg)
A former seventh-rounder (and over-slot signee) for the Oakland Athletics in 2009, Krol transitioned from the rotation to the bullpen last year and has thrived in that role this spring for Double-A Harrisburg. Though he boasts a three-pitch mix, Krol currently works primarily fastball/curveball, with the heater sitting low-90s and capable of reaching 94. As a starter, the former Illinois prep standout had difficulty turning over a lineup and struggled to limit free passes. He has limited the negative affects of his somewhat violent delivery in relief, while seeing an uptick in his stuff in short spurts. With improved velocity to go with his sharp 1-to-7 breaker, Krol projects well as a seventh-inning arm that is particularly tough on lefties but capable across his splits. With just two runs allowed through his 26 innings of work this spring, Krol could soon be a candidate for promotion, with a chance to help out the big club later this summer. His spotty command still forces him to work deep into counts, and he’s probably not a multiple-inning arm at the top level, but he should have value, which was far from a certainty just 18 months ago. —Nick Faleris
Chris Owings, SS, Arizona (Triple-A Reno)
Reno is a nice place to hit, but what Owings is doing with the stick isn’t just a product of the friendly environment. The 21-year-old shortstop is a highly skilled all-around player, with natural pop in the bat and good fundamentals in the field. He’s not going to crush you with elite-level tools, or even tools that force scouts to get crazy with the sixes (plus), but he can execute in game action and he has the ability to play a premium spot on the diamond. While he’s unlikely to force Didi Gregorius off the position, Owings has the offensive upside to slide over to second and make it play; he could end up a .270 type of bat with 20-plus home run pop. The approach is aggressive and could force the hit tool to play down, and it remains to be seen how he will adjust to major-league quality pitching—the kind of pitching that looks to exploit aggressive bats early and often. But Owings has the type of versatility and game skills to find a home at the major-league level for a very long time, with a chance to blossom into a role-6 player (first-division) if everything clicks. —Jason Parks
Stryker Trahan, C, Diamondbacks (Extended Spring Training)
Arizona’s top pick in 2012, Trahan posted a .281/.422/.473 slash line in 49 complex-league games last summer. While his advanced left-handed stick is ready to handle full-season pitching, his game behind the plate is a major work in progress. For the time being, the D’backs are holding the 19-year-old back in extended spring training to focus on his catching. I’ll be featuring Trahan later this week at Baseball Prospectus in my extended spring training scouting notes. For now, here’s video of the first-round pick in game action last week —Jason Cole
Angelo Gumbs, 2B, Yankees (High-A Tampa)
After a slow start and a trip to the disabled list with a sprained finger, Gumbs is once again showing flashes of the skills that made him the seventh-ranked prospect in the Yankees farm system coming into the year. Gumbs is a gifted athlete with fast hands at the plate and the type of bat speed that creates exit velocity that makes scouts scream and cry like teenagers at the Cavern Club. But Gumbs’ game is far from refined, with an aggressive approach that limits the utility of his bat and a competitive edge that can run hot enough to affect his play on the field. At the end of the developmental day, Gumbs could find himself in the outfield, where his plus speed and athleticism could make him an above-average force, and if the approach matures and the hands continue to receive praise, the natural bat-to-ball ability and strength could make him a legit majo- league bat, perhaps one with the potential to hit for both average and power. —Jason Parks
Nick Castellanos, OF, Tigers (Triple-A Toledo)
After a slow start to his 2013 campaign, Castellanos has shown steady improvement at Triple-A Toledo, producing more frequent hard contact over the last month and generally looking more comfortable in the box as he continues to adjust to the level. Over the course of his professional career, Castellanos has worked to improve all facets of his offensive game, and that progress has continued this spring, with a noticeable jump in his batting average/on-base delta, in particular. With the former first-rounder just a hair over 21 years old and already finding success at Triple-A, the Tigers have little reason to rush Castellanos to Detroit. He projects as a 6-plus to 7 bat that should grow into plus playable power (perhaps better) as he continues to fill out. He already excels at producing contact at optimal leverage points, helping him to drive the ball with ease from pole-to-pole. He continues to work on his reads and routes in the outfield, and should be an average defender there in time. —Nick Faleris