Yep, the guy is a beast--surely one of the 4-5 best RPs in your world. If you were to trade him, you should get a very substantial return. About his current underperformance, I don't believe I have any supporting evidence, but I have a very strong suspicion that how many pitches a pitcher has matters the more innings he pitches. If you found a pitch count that kept him under 2 IP per game (my guess for him that's somewhere around 30), I bet his ERA would go down. In the long run, you may have to choose 200 IP of ~4.00 ERA or 130 IP of ~3.00 ERA, because I think he is capable of either one..