Much was at stake in this fierce North West clash as both teams try to play catch-up at the top of the Premiership.
United got just the result they were looking for and Liverpool were left with a huge blow to their confidence as well as cuts and bruises by the end of this hard-fought battle.
Tempers flared from the outset with a number of over-zealous challenges pleasing the baying crowd, but the referee failed to call them and struggled to impose his authority for the rest of the game.
The latest addition to Anfield's Spanish armada, Fernando Morientes, looked eager to impress from the start but the first time he found the ball at his feet in United's area, he dribbled the wrong way to escape two defenders and lost the ball.
He gave Liverpool some much-needed height up front but looked tired on the day and often made wrong decisions as he struggled to adapt to the Premiership's unique style of play.
The Real Madrid export came close to scoring minutes later from a pin-point pass from Steven Gerrard, but his header was snaffled up by Roy Carroll.
Milan Baros looked lively, running at defenders and keen to stay in his bosses' good books with the arrival of another star striker.
Young Rooney looked isolated on the right-hand side and frustrated at his team-mates' passing ability during the first 20 minutes.
But the precocious teenager should never be underestimated and scored with virtually his first touch of the game.
On his first foray into midfield he collected a quick ball from Cristiano Ronaldo and dribbled unchallenged towards goal.
The England striker broke the deadlock with a low shot to the near post, which Jerzy Dudek should have saved, had he been more alert.
Liverpool were stunned and struggled to regain their composure as United went on the offensive and took full advantage of the Merseysiders' sleepy start.
Roy Keane finally gave them the slap in the face they needed, but it would have cost them another goal if it wasn't for the woodwork.
United's veteran captain received the ball from Paul Scholes 30 yards out and looking up as though he was going to pass, decided to have a crack himself.
But his looping right-footed shot hit the underside of the bar and nearly went in off the back of a hapless Dudek.
Liverpool's iron man Gerrard yet again provided the inspiration for his side's resurgence by chasing back to win balls in defence and pushing them forward.
The home side's best chance of the half came when Gerrard found Morientes wide open with a pass round the back of Wes Brown, but his shot spooned wide of the mark and he trudged off the pitch at half-time knowing he could have levelled the score.
The ref continued to court controversy as the second half got under way as Liverpool tried to get back in the game.
United resorted to bully tactics to hold on to the lead and were getting away with too many fouls in the referee's line of vision.
John Arne Riise managed to find Morientes with a clever side-footed pass, but he was blocked inside the area by Gabriel Heinze, as he turned to threaten goal.
Penalty cries rang around the stadium, but no foul was called much to the Kop's continued vocal disgust.
Moments later Baros had to leave the field for treatment to a head wound after being felled by a touchline challenge and getting a stud tattoo across his forehead.
He finally produced a second yellow card for Brown's late tackle which knocked Riise flat on his back, but only after loud protestations from Gerrard and Sami Hyypia.
But even with their fierce rivals reduced to ten men, it was too little too late for Liverpool and the game ground to a halt as United dropped back to defend their lead.
Man of the Match: Roy Keane - Constant force in defence, terrorised Liverpool's midfield and disrupted their normal passing game.