Kompany and whoever plays at right back are the main problems at the moment imo.
Nastasic was clearly the better of the two CBs last night, and at 19, looks an amazing prospect. I think he's ready to play at this level, so he should get all the opportunities he can.
Kompany's been the main problem so far, and I don't think it's as simple as saying he should be playing beside Lescott - he's played badly alongside Lescott this season, too.
And I think the RB is the problem - ok, Maicon was owned by Tranny, so was Zaba. But Zaba was also out of position quite often yesterday - way forward, and that must really freak Kompany out. He has occasional flashes of brilliance, and usually recovers well, but I'd rather have a cast iron back four again, even if it means the FBs don't get forward quite as often. The problem is that no one else in the team is expected to provide that width.