I don't know if he has improved on hitting breaking balls since being drafted, but his K/AB ratio has improved every year while his walks have remained basically the same, maybe with minimal improvement. The K/AB ratio still isn't good, but if he keeps improving it like he has been, it soon will be. But, you're right, if he indeed does struggle and continues to struggle with breaking pitches, then he'll have a hard time continuing the trend of improved Ks per ABs.