Liverpool goalkeeper Jerzy Dudek suffered another nightmare against 10-man Manchester United as they secured a vital victory at Anfield.
Dudek allowed Wayne Rooney's tame 25-yard shot to slide in after 22 minutes to gift the former Everton striker a goal in front of The Kop.
United deserved their victory, despite having Wes Brown sent off for two bookable offences after 64 minutes.
Roy Keane hit the bar, while Fernando Morientes had a quiet debut.
It gave United a crucial win as they continue to keep up the pressure on Premiership title pace-setters Chelsea and Arsenal.
Liverpool gave first appearances to £6.3m striker from Real Madrid Morientes and Mauricio Pellegrino.
But United suffered injury setbacks when Alan Smith and Rio Ferdinand were ruled out, while Ryan Giggs was still absent with a hamstring problem.
Liverpool dominated the early stages, but were stunned when United were gifted the lead by Liverpool goalkeeper Dudek.
Rooney cut in from the left and tried his luck from 25 yards, Dudek appeared to have the shot covered but somehow let it slip behind him into the net.
It was the latest calamitous error by Dudek against United, following mistakes that gave Diego Forlan two goals at Anfield two seasons ago and errors when Giggs was on target in their victory last term.
And only the crossbar prevented United doubling their advantage seven minutes later when a spectacular dipping drive by Keane hit the woodwork and bounced to safety.
Liverpool's momentum had been halted by the goal, but there was a fleeting glimpse of Morientes' aerial ability two minutes before the interval, when he rose to meet Luis Garcia's cross but was off target.
There was a potential turning point after 64 minutes when Brown was shown the red card for a second bookable offence, this time for a reckless challenge on John Arne Riise.
Ferguson immediately made a change, sending on John O'Shea for Cristiano Ronaldo.
And as the temperature rose, Rooney was booked for taking as kick at Garcia after a tackle.
United goalkeeper Roy Carroll, restored after "the goal that never was" against Spurs at Old Trafford, made a crucial save in injury time, blocking Jamie Carragher's shot from the edge of the area after Gerrard's free-kick.
Liverpool: Dudek, Carragher, Pellegrino, Hyypia, Traore,Luis Garcia, Gerrard, Hamann (Biscan 79),Riise (Sinama Pongolle 72), Baros, Morientes (Nunez 75).
Subs Not Used: Warnock, Harrison.
Booked: Carragher, Nunez.
Man Utd: Carroll, Phil Neville, Brown, Silvestre, Heinze,Fletcher, Keane, Scholes, Ronaldo (O'Shea 67),Rooney (Bellion 90), Saha (Fortune 79).
Subs Not Used: Howard, Miller.
Sent Off: Brown (65).
Booked: Brown, Rooney, Fortune, Keane.
Goals: Rooney 21.
Ref: S Bennett (Kent).