http://www.fangraphs.com/statsd.aspx?playerid=11426&position=P
So far, he's had two s***** starts, three really good starts and lots of mediocrity. As a fifth starter, you can do much worse. If they didn't trade Espinoza for him, I'm sure there'd be much less talk about how mediocre he is.
My biggest concern with him is durability.