His legs haven't completely gone at all, we heard the same from people on this forum a few weeks ago about Aguero which, likewise, wasn't true. He's not fully fit and fully sharp, I'd agree but that's because he's not playing regularly. Your legs don't go overnight - at the end of last season, he was one of our best players. He just doesn't play in a system that suits him. Unfortunately for him, City are a better team in that system but if he was to play in a team that suited that system, he'd still be one of their best players.
And doesn't contribute to our play in any way? 91.9% passing accuracy was the best on the pitch by any midfielder, and very impressive given the way that Bristol pressed us. He also, unusually, made a couple of important defensive headers which I haven't seen from him in years. He had a good game against Bristol, the stats bear that out.