United must shake off the 2-1 loss with Chelsea to visit Old Trafford on Saturday.
"We had all night to think about what went wrong," said Vidic. "It was not a great game for us. We should play better and we will need to play better against Chelsea.
"Sometimes when you lose a game and play badly you wake up and realise you need to improve."
That improvement is possible, with Ryan Giggs and Antonio Valencia the most obvious replacements for Rooney and Paul Scholes, who has now played two matches in four days and convention suggests he will not be asked to put his 35-year-old body through a third on Saturday.
But the pall of Rooney will hang until such time as United prove they can operate without him.
Beating Chelsea and Bayern would do exactly that. And Vidic is quietly confident.
"I am not concerned. I was disappointed," said the Serbian.
"But 2-1 is not that bad a result bearing in mind we still have a game at home and I expect us to be stronger."