The striker, scorer of the winning goal in this year's European Championships final, was anonymous for much of the evening as his partnership with £20m new boy Robbie Keane continued to stutter, but he produced a vicious drive eight minutes from time to claim the points.
It was a bitter pill to swallow for a Sunderland side who had enjoyed the best of the play and all but negated the return of the Reds' fit-again skipper Steven Gerrard.
Sunderland handed out four debuts - with former Reds winger El-Hadji Diouf joining Teemu Tainio, Steed Malbranque and Pascal Chimbonda in the starting line-up.
The Black Cats immediately went on the attack, Diouf powering straight into the Liverpool half before losing the ball at speed.
Malbranque was also eager to make an impression, nimbly turning Yossi Benayoun but chipping his through-ball just too long.
With just five minutes gone Diouf pace had worried his former side twice, first drawing a last-ditch tackle from Jamie Carragher and then forcing Jose Reina into an ill-judged clearance.
Liverpool attempted to force their way back into the game, Gerrard drifting out wide as he twice tried and failed to play in Keane from the right.
Diouf, enjoying quite a start to a Black Cats career, proved more incisive after 13 minutes, taking advantage of some sloppy defending to cross for Daryl Murphy but the Irishman headed straight at Reina with the goal gaping.
Gerrard then prevented another attempt on goal when he stole in to dispossess the Kieran Richardson in the box.
Sunderland briefly lost their composure after 25 minutes when the unlikely figure of Sami Hyypia caused a mix-up between goalkeeper Craig Gordon and his defence although Liverpool's attackers were unable to take advantage.
Referee Alan Wiley decided not to award a penalty after a heavy collision involving Benayoun, instead blowing for a foul on Gerrard moments before. The resulting free-kick was in a promising position, but a telegraphed routine from Keane and Gerrard ensured nothing would come of it.
Keane made a better fist of a half-chance three minutes before the interval but screwed his shot wide after skilfully setting himself up.
Benitez swallowed a certain amount of pride during the break, withdrawing the ineffectual Damien Plessis and installing Xabi Alonso - a player the Spaniard is happy to sell for the right price - in the centre.
After 54 minutes, former Bolton man Diouf spurned a fine chance.
Murphy, making amends for his earlier miss, laid the ball tantalisingly across goal only for Diouf to scuff his shot to a grateful Reina.
Alonso gradually started to rouse the Reds, elegantly starting a move which ended with one of their better chances - a Gerrard shot cannoning off Danny Collins on the six-yard line.
With 20 minutes to go, Benayoun won a free-kick a yard from the edge of the penalty box - but again Gerrard's delivery was tame.
In the aftermath, Keane and Torres' fledgling pairing - which struggled in the 0-0 midweek draw at Standard Liege - reached its lowest point yet, the Spaniard turning a loose ball goalwards only to see his partner unintentionally deflect the ball out of play.
Keane was taken off, his name sung loudly by the home fans, minutes later.
An Alonso special from within his own half almost settled the match in spectacular fashion, but the midfielder was just wide with his strike - much to Gordon's relief.
It was Alonso's touch too that freed his compatriot after 82 minutes - but the finish, swerving at pace, was all Torres.
Sunderland: Gordon, Chimbonda, Nosworthy, Collins, Bardsley, Malbranque (Edwards 73), Tainio (Whitehead 57), Reid, Richardson, Diouf (Chopra 81), Murphy.
Subs Not Used: Ward, Leadbitter, Higginbotham, Stokes.
Liverpool: Reina, Arbeloa, Carragher, Hyypia, Dossena, Kuyt, Gerrard, Plessis (Alonso 46), Benayoun (Aurelio 81), Keane (El Zhar 77), Torres.
Subs Not Used: Cavalieri, Agger, Ngog, Skrtel.
Booked: Arbeloa, El Zhar.
Goals: Torres 83.
Ref: Alan Wiley (Staffordshire).