That is exactly correct. When he has control his ERA reflects dominance. Here are the details of his K/BB and how they relate to his ERA:
2007: 26/14 ERA: 3.43
2008: 8/17 ERA: 6.39
2009: 41/23 ERA: 4.50
2010: 27/24 ERA: 6.28
2011: 42/19 ERA: 3.69
2012: 37/9 ERA: 3.12
I am not saying that Morales is the only pitcher in the world where his success correlates so directly with his K/BB ratio, but the above statistics do show that when he can limit his walks, he is always dominant with ERAs less than 4 when his ratio is near 2:1. He is certainly worth a shot at stretching him out so he can replace DiceK in the rotation.