Arismendy Alcantara is a small middle infielder (listed at 5-10 160) that was signed out of the Dominican Republic by the Chicago Cubs in 2010.
He has been used almost exclusively as a pinch runner/pinch fielder in the Dominican Winter League, but did get an at-bat on Wednesday night (in which he grounded out to end an extra inning game). Even with the platoon advantage (he is a switch hitter who was hitting right-handed against a left-handed pitcher), he didn't seem to have very good plate discipline and he sometimes come out of his swing.
He is not a player that ever really appears in Cubs' prospect lists but he played in A + as a 21 year old (actually he was 20 for the whole actual season). The average age in the Florida State League was 22.7 years old. Despite this, he had a good year with the bat, with a 110 wOBA + and 124 OPS +. This was good for 30th in the league in wOBA (out of hitters with at least 300 plate appearances). More impressively, Alcantara was younger than 26 of the 29 above him. The Cubs Florida State League affiliate Daytona played basically neutral in 2012 (99 one year Park Factor), but he was much more effective at home than he was on the road (the ISO was basically the same, the difference was mainly BABIP). His switch hitting is paying off as well, as he was equally effective from both sides according to OPS in 2012, with better peripherals as a right-hander and more power as a left-hander. He seems to be an average/BABIP dependent hitter, as he doesn't walk much (doesn't have a big strikeout rate, but it is too high for his walk rate) and doesn't hit for much power. He is a ground-ball hitter, though his ground-ball rate did drop in 2012. At the plate, it seems like he has some work to do mechanically. Despite taking no real stride, he loads up with a front leg kick. This isn't the best way to start and he doesn't have a swing that would make any opposing player jealous. I actually saw some video of him before 2012, and it seems that he did not have this load. Perhaps it is ironic that he had a better season with it, or perhaps it is a timing mechanism that works for him.
After stealing just 8 bases and being caught 8 times in 2011, Alcantara was much more efficient in 2012, stealing 25 bases and was caught just 4 bases. Part of the struggles in 2011 may have to do with leg injuries, as he has had DL stints in each of the past 2 years. However, one would not have expected him to have had the success on the bases he had in 2012 if they were bothering him. Overall, you are seeing improvements in his overall game, as his ISO, Stolen Base success, and Speed Score have all went up over his 3 years (without repeating levels), and he has been dropping his strikeout rate as well (I am not counting 2009, as he spent the year in the Dominican Summer League, which is somewhat of a different animal statistically). His speed score was 8.1 in 2012, which was 2nd to only teammate Matt Szczur in the Florida State League (it was also in the top 40 in the minor leagues as a whole, tied with Brett Jackson and Jimmy Paredes). Basically, he is fast, and a good baserunner as well (Baseball Prospectus gives him a positive baserunner and the Baseball Cube gives him a 85 out of 100 on speed).
Both the data (RTZ, FRAA, and Range Factor) and the scouting reports say he needs to work on his defense. However, he played almost exclusively shortstop in 2012 (after splitting time better short/2B/3B in previous seasons). While athleticism obviously does not always translate to good defense, both his age and speed at least give you a reason to think that he will improve.
Whether or not his defense develops determines whether or not he is a MLB player for me. If he becomes at least a decent to average defender, he could be a slap hitting utility infielder that you could use late in games on the bases. Because his plate discipline needs so much work, I have to imagine that he is going to find AA in 2013 pretty tough.