Keep in mind that this is not a traditional top prospect list because it focuses entirely on 2014 contributions. I rank guys according to advanced metrics which, for position players, include batting runs above average (now from Fangraphs), positional adjustment, and a replacement level calculation that scales the total to "Wins Above Replacement" (though the concept of replacement level doesn't really apply to minor leaguers, obviously). Defense is a best guess, though I'd like to think it's an informed one. I use a standard "runs allowed based" WAR formula for pitchers for the ranking, but include FIP-based WAR for comparison.
31. Alfonso Alcantara, 21, A. RA-9 WAR: 2.1, FIP WAR: 1.9, 125.1 IP / 3.81 ERA / 22% k-rate / 11% bb-rate / 58% GB rate
Alcantara consistently sat in the mid 90's while touching higher last year, and his power secondary offerings - a change and slider, both in the 88-90 range - became true weapons. It's an ace-caliber arsenal, even the secondaries. The quality of his stuff doesn't show up in traditional K%-BB% analysis, but it's clear as day in his batted ball profile: righties and lefties alike struggle to achieve any lift, failing to leave the infield more than 60% of the time on contact. Doing that against just same-handed hitters puts him in good company. Doing that against opposite-handed hitters too makes him an outlier. Geared up for the extreme heat, it was all A-ballers could do to roll the ball over to shortstop or second.
What he lacks are pretty mechanics and consistent command, but a dominant fastball and two strong secondaries could make him a spectacular-one-night, painful-five-nights-later type of mid rotation starter. Or, he's a power reliever in the Jordan Walden/Kevin Jepsen mold. Regardless, he's probably the best right-handed arm left in the system. Baseball America ranked him the system's sixth best prospect, while ESPN's Keith Law put him at seventh.
Here's a bootleg video of his delivery. You're welcome. He's currently always throwing from the stretch.