United have failed to score in their past two matches and Rooney is ready to take his frustration out on City.
Rooney said: “It’s not worrying.
“I hope we’re saving the goals for Manchester City.
“The derby at the weekend is a big game for us and we’re all looking forward to it.
“I’m not quite sure the draw with Villarreal was one for the spectators, but we were probably the better team and we created lots of chances.
“We just couldn’t take them. The main thing is we’re through to the knockout round.
“We’ve got one game left against Aalborg and if we win that we will finish top of the group.
“This result could be good for us in the end.
“I don’t know why we keeping drawing 0-0. In most of the games we’ve been the better team.
“They defended well and they’re not all that enthusiastic to win the game, so that makes it more difficult for us.”