Manager Sir Alex Ferguson was in shock four months ago that his top forward wanted to leave but the England international had a change of heart and penned a five-year deal that ensured he would not be one of the huge transfers of the January window.
Rooney's double in the 3-1 victory over Aston Villa on Tuesday could open the floodgates for a player who scored 34 goals last season.
"Hopefully I can go on a good run and help the team win games," Rooney told MUTV.
The resurgence of Rooney, who knows his club inside out, would come at the right time as United seek a record 19th English league title, while Chelsea's record signing Fernando Torres settles in to Stamford Bridge.
The fact that United have built a five-point lead at the top during Rooney's lean spell, also caused partly by injury and off-field problems, bodes well for their title hopes.
"They have managed to win a lot of games and remain unbeaten without him," Villa manager Gerard Houllier said referring to United equalling a club record of 29 league matches without defeat.
"With him, wow. He was on top of his game today. He had everything. He can control, turn, twist, play the pass. He defends, he works hard. It was an example for what kids should do - the workrate and link play, everything."
Chelsea sought to remedy their problems in the January transfer window by forking out a reported British record of £50 million to buy Torres, while City spent around £30 million on Bosnian forward Edin Dzeko.
United, meanwhile, steered well clear of what Ferguson has described as "inflated" fees, simply adding Danish goalkeeper Anders Lindegaard to their books for a modest £3.5 million.
"Wayne hasn't scored a lot of goals recently but he's been very important for the team," United winger Nani told MUTV.
"Sometimes things don't go the way he'd like them to but I think tonight was his best performance of the season. From now on he'll be very important for the team."
