I don't think he's useless, but he's very much a form player. He's a nail eating monster when he's on form, but he inevitably loses form and turns into a headless chicken with a penchant for the kamikaze. His best season was Kenny's full year, but even then he had some pretty shocking games. Remember the shocker he had that ended in a red card against Spurs? I don't know how many call for his head there were after that one.
I think it's great that he's fighting for his place, and if the competition has made him a better player, then great, but I wouldn't be that surprised (or even that terribly disappointed) if he left in January for a good price. Sakho and ilori will be enough, I think.