Drogba struck twice in last night's 2-2 draw with Atletico Madrid.
He said: "It is really important for us to beat United at home. We have to improve and show different qualities and be better than we were in Madrid.
"The match against Atletico was far from a good performance, we played well but were not good enough to win. I think we were thinking about Sunday's game. For their equaliser we could have done better with the wall and maybe avoided the free-kick. It's frustrating to concede a goal like this after the efforts we produced."
Drogba, who missed the first three games in Europe through suspension, is full of confidence after scoring 12 times in his last 13 starts. He said: "I think this is my best period for Chelsea. A few years ago I was playing with the same confidence. It's always easier when you are playing injury-free."