I think Milner is also a key player here, that we could really do with for the derby. Competitive, and delivers a good ball.
If he and Silva both make it, there's the problem solved. If not, probably Nasri + Silva / Milner. If no Silva or Milner, can see us going with 4-3-3 which becomes a 4-5-1, with Barry, Yaya and possible Garcia rather than Nasri in the middle, and Tevez, Balo and Sergio as a forward three, dropping back when we don't have the ball.
Defensively I think it's clear that we want Zaba and Clichy at full back, as they'll likely start with Young and Valencia wide (Valencia's supposedly 50/50, so you know what that means), though I do have slight concerns about pace if Zaba comes up against Young. Nastasic would get the nod from me, his movement is better and he is more comfortable on the ball, though he may be a little more naive which they will try and play on at every chance (handball ref! etc etc).
Means we have to dominate their middle two, likely to be Carrick and either Fletcher or Scholes. They'll have fat boy dropping back to mark the ref and bully our def mids, and either Welbeck or Sh*tpea up front. Stop them getting the ball out wide by dominating the middle and they can only play in front of us.
Just a case of who up front then - Tevez and Balo? Tevez and Sergio? Dzeko? Sergio and Balo like the 6-1? Whoever it is, they need to get their shooting boots on as if we get the first goal we'll have a very good day.
Tonight may give us the biggest clue as to who will start, and it will be playing in Mancini's mind that Silva may not make it, so does he rest players that Silva plays best with, or rest players than can replace him?
That said, I do hope David makes it. He makes us tick, his close control is amongst the best in the world 9 times out of 10. But if he's not close then don't even have him on the bench - rather have him fit for the rest of our schedule. United will drop points elsewhere anyway, am sure of it.