He did not have the cutter which is frankly what has rescued his career. His fastball was never effective, but the pitch sequence has changed things.
Now, he has 111 IP over 4 months basically since his TJS. If the market thinks he can deliver ~500 innings at the clip he provided this year, that's probably a 20 million dollar pitcher. I mean that amply described Porcello - and that deal has worked out reasonably. (not GREAT, but reasonably)
Right now the best thing he has going for him is that he did not wear down this year and made all of his starts, and finished strong. I would not blame the Red Sox if the bidding got too hot for, say, deciding a healthy Pomeranz and then diving into the Derek Holland/Anibal Sanchez/Matt Harvey pool would be a better use of resources.