Over the last three seasons, he's had the highest K/9 of any starting pitcher at 10.12. Lincecum is second at 9.79. And since coming to Toronto (as already mentioned), he's had FIP/XFIPs at least a run better than his actual ERA.
I'll always be a buyer on him, especially considering those peripherals. Now it's possible that this is a trend and he'll never bring his fantasy stats in line with his underlying metrics, but at his ADP, I don't really see an SP with that upside.