The 26-year-old believes the game at Molineux will be tough as their opponents are 'fighting for their lives' and insists the Red Devils will need to be in good form to win
Sir Alex Ferguson's men crashed out of the Europa League on Thursday night, suffering defeat to Athletic Bilbao, however, they lead their rivals by one point in the title race.
The 26-year-old scored a double in the 2-0 win over West Brom last weekend and is hoping his side can run out victorious again on Sunday to extend its lead at the top.
The Englishman told the club's official website: "It's a massive game for us, particularly given that Manchester City don't play until Wednesday. We have a chance to go four points clear at the top of the table and we have to get the win."
Wolves currently sit just one point ahead of bottom club Wigan at the other end of the pile, however the forward insisted that traveling to a side battling against relegation is never easy.
"We've had tough games there in the last couple of seasons and we need to be at our best to win," he added. "Wolves are fighting for their lives after going through a bit of a sticky patch and seeing Mick McCarthy leave.
"I'm sure it's been hard for Wolves to lift themselves, but from our point of view when you go to the home of a team fighting to survive it's always very difficult. So we know we need to play well to win."
Rooney has been in outstanding form this season, hitting 20 goals in 24 league games.
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