IMO, his gamebreaking ability was his shot. Not the PP one timer from the point, but those where he just rips it top shelf from out of nowhere. Basically unstoppable. That shot has been completely missing, and I wonder if it's injury related or not.
Hard to get his shot away if he can't create separation. Its hard to create separation when you can't generate speed or pivot away from checks.
I think Petey has been really good at finding ways to be productive despite his limitation, but he is definitely still limited by something (his knee, or confidence, or "lack of moving his feet", or a combination of them).
I'm actually very impressed that he has found a way to be productive when he is not able to skate as well as before. That is like one of the major factor causing the older players' decline, when they lose their speed they are done. Petey somehow found a way around it, I think he deserves a lot of credit for that.