The Norwegian struck his first goal of the season to give the Reds only their second away league win.
Liverpool, now unbeaten in six Premiership and Champions League matches, are beginning to climb the league table. Though it was a case of grinding out their latest success at City.
While Liverpool are on an upward curve City are on a slippery slope having only won once in their last five league matches.
They had precious little to offer up front with Liverpool keeper Jose Manuel Reina having only one save to make in entire match.
It is a concern for manager Stuart Pearce who said: "I couldn't fault the effort of my players and point the finger at anyone to say they had let us down.
"What we lacked was quality ball to Andrew Cole and Darius Vassell and we failed to get into positions to hurt Liverpool.
"They are the Champions of Europe. They didn't dominate, but maybe they had more possession."
Pearce added that he considered his side's performance would have been good enough to win between 60 and 70% of games and Pearce also commented on the minute's silence in memory of George Best, which had to be cut short by ref Alan Wiley because of the jeers of fans.
He said: "I am not sure which fans were responsible but the vast majority in the stadium paid tribute to a legend who has given a lot to football. I think the important thing is to take the positives rather than harp on about one or two negatives that happened around the crowd of 47,000."
Liverpool lad Joey Barton returned after suspension for City, replacing Sun Jihai in the centre of midfield, the one change from the previous week's match against Blackburn.
Bolo Zenden was ruled out through injury, Morientes dropped down to the bench as Benitez recalled Djibril Cisse and Stephen Warnock to his side.
City carved out the first clear cut chance in the 13th minute when Vassell headed wide from eight yards when he ought to have hit the target following a left-wing shot from Kiki Musampa.
It was a rare moment of excitement in what was developing into a dour match which was completely devoid of any goalmouth action, with both defences firmly in control.
Liverpool had to wait until shortly before half-time before creating their first decent scoring opportunity.
Captain Steven Gerrard cut in from the left past defender Richard Dunne and curled a shot inches wide of the far upright.
City were incensed claiming Gerrard handled the bal but ref Wiley pointed for a dead ball so it would have been a goal had Gerrard managed to hit the target.
Benitez made the first change of the match with six minutes of the restart, bringing on Kewell for Cisse.
Liverpool keeper Reina was not called into action until just short of the hour mark when he was forced to make a decent save to keep out a long-range shot from Vassell. The deadlock was finally broken in the 61st minute when Liverpool took the lead.
Riise played a return pass with Gerrad and struck a wonderful left-foot shot from outside the penalty area high to the right of keeper David James.
Crouch joined Cisse in ref Wiley's notebook following a clumsy challenge on Barton.
Pearce brought on the fit again Trevor Sinclair for Musampa with 22 minutes remaining to try and provide better service for the strikers. That was soon following by the introduction of Sun Jihai, who replaced Stephen Jordan while their last throw of the dice was to bring on Bradley Wright-Phillips in place of Danny Mills.
But despite a spirited finish City failed to create a clear cut chance and Liverpool were never seriously challenged.