With the 'giddyometer' threatening to spin out of control ahead of the derby, Mancini has warned that Villarreal must be the sole focus.
"It is important for us to concentrate on Villarreal." Mancini said. "If we can beat Villarreal - and I don't think it will be easy - maybe we will have a better chance to go through to the knock-out stages. If we don't beat them, it will be difficult." So is it really a bigger game than the clash against United on Sunday?
"Yes," Mancini said. "After Villarreal, we have four days to recover and to prepare for the derby. We don't really need to prepare for the game with United because we know they are a top team, and I don't think we need to prepare any differently. Beating Villarreal is our first target. Then we can think about the other games.
"We are playing in the Champions League for the first time and we can't think that we will win every game. We know we need more experience, but we still have four games left and, if we beat Villarreal, we can still get first place in the group. If not, we can fight for the second place."