He's good at what he does, but he's not perfect. See Ryan Madson last year. Also see Lohse earlier in his career. The Phillies offered him something like 3 years/21-24 million to stay, he rejected it, the Phillies moved on, and there wasn't a market for him so he signed at 1 year, 4.25 million. Now, it ultimately worked out because he had a career year and got 4/41 from the Cardinals the next offseason, but I'm sure that wasn't really how he drew it up.