He hits too many groundballs to put up elite power numbers (62% on the ground, and a mediocre 46% last season). I hope he develops a more advanced plate approach in the future--right now he basically is just doing the ol' see the ball, hit the ball "method." He really needs to work the count, get pitchers to make hitters' pitches in the fat part of the plate that he can drive.
That's been a big problem w/ him in the past--he never really had plate discipline but playing against inferior physical talents he could still slam some bad pitches out of the park. Unfortunately, unless you have Vlad Guerrero-type talent, you aren't going to do that in the major leagues very regularly.
The good news is that he's trending upwards: 2.9 in first year callup, 3.5 last season, and 3.9 this year. 3.9 is actually really good, so if he maintains that kind of patience we should eventually see his FB rate increase and the homers to come.
I still like him for .280/15 HR/70 RBI for the remainder of the season.