I like EBJ a lot, but he is certainly going to need to hit for more power than he showed in his brief professional debut last year to be a starter in the big leagues. Now, I think that he will and it seems most scouts have that opinion as well. We aren't talking home runs here, but he needs gap power and the ability to rack up some XBH.
3 extra base hits in 110 minor league plate appearances just won't cut it. If he doesn't improve on that and ML pitchers know that the worst he can do is flare a singe over the shortstops head, outfielders will play way in and pitchers will just attack. The walks will decrease significantly. If you have elite plate discipline, it's easy to rack up walks in the low minors without any power. There are too many pitchers with horrible command that couldn't challenge you if they tried.
Again, I think he is going to improve on that. However, he'll need to do much better than a .038 ISO to be a ML starter.