Mock is wonderful. I don't know why he couldn't have been that good as a starter, but we kind of needed help with out pen anyway.
I love Mock. Thankfully Manning didn't waste that replacement move. When they IBB a guy and bring you in to face one lefty batter, you better get him out. Mock will certainly get a look as a starter again, but right now, he is effective as a good reliever that provides a lot of options in terms of how he is used.