Their bitter neighbours looked to be running away in the title race at the beginning but Sir Alex Ferguson's men clawed their way back in it - closing the gap at the top to just two points at Christmas.
And United even have the chance to knock City off their perch on Monday should they beat Wigan at Old Trafford and Roberto Mancini's men lose at West Brom.
Reflecting on the events in the first-half of the season, Rooney praised his side's comeback in the title race.
"It is an amazing turnaround," the England striker told Sky Sports.
"Last season we only dropped two points at home but struggled away.
"This season we've already dropped five points at home but we're making up for that away."
The Red Devils have an easy year-end run in with home games against Wigan and Blackburn.
But their task has been made tougher with news that Ashley Young will be missing until the new year with an injury sustained in the Fulham win.
Phil Jones will be available, however, after fears that a jaw injury could keep him out.