I think two of the reasons for why he wasn't "on form" with us is: 1. Torres kept getting playing time ahead of Ba, although we all know Floppes is not as good. 2. In Newcastle he was the main man, players would specificaly look for him when on the ball, but here we have Mata and Hazard and Oscar who love keeping the ball, dribbling, creating chances for each other.. so the system is also different + he gets less opportunities. I don't think saying Ba "failed" at Chelsea is fair. He did a descent job and I'm sure he'll come of good this season.