Manchester City manager Roberto Mancini was left feeling as though he had been mugged after Manchester United left it late to confirm their Carling Cup final place.
The all-Mancunian semi-final was heading for extra time until Rooney popped up to nod home his 21st goal of the season to secure a 3-1 win and complete a 4-3 aggregate triumph.
Goals from Paul Scholes and Michael Carrick had put United 2-0 ahead but old-boy Carlos Tevez stunned Old Trafford with a strike 14 minutes from time before Rooney settled matters.
Mancini said: "After our goal I did not think it was possible for us to lose. I am very disappointed because, apart from 10 minutes, we played very well.
"But next time we will have to pay more attention because Wayne Rooney is one of the best strikers in the world. If you give him a chance to score he will take it."