Two knee operations at the back-end of last season and a late return from the World Cup have impacted on the 26-year-old's fitness and match sharpness.
But a clinical strike midway through the second half - his first Premier League goal since March 28 and 50th at Anfield in all competitions - proved too good for promoted West Brom.
Torres was rested for the midweek Europa League play-off trip to Trabzonspor and the decision was justified with victory in Turkey without him and, more importantly, rewarded with the winning goal against the Baggies.
He had not scored in 10 matches for club and country coming into this game as he has been working his way back to fitness but even a 75% fit Torres provides a threat for opposition defences.
Torres had three half-chances in the opening 45 minutes but none could have been classed a genuine opportunity.
His first in only the third minute was curled straight into the arms of former Liverpool goalkeeper Scott Carson before a close-range strike was then crowded out at the near post.
His third sight of goal, in the 15th minute, was an indicator of where the Spain international is in terms of sharpness.
Martin Skrtel's header sent Milan Jovanovic charging down the centre of the pitch but Torres was half-a-yard short in reaching the pass as a sliding Gabriel Tamas cleared the danger.
Liverpool dominated possession but there were a couple of occasions when West Brom threatened to make them pay.
Marc-Antoine Fortune, making his first appearance for the club since he returned from Celtic, fired in a low shot which goalkeeper Jose Reina collected at the second attempt while late in the half James Morrison sliced a long-range shot just wide.
New signing Raul Meireles, given the number four shirt vacated by Alberto Aquilani's loan to Juventus, would have been hugely underwhelmed by what he saw.
It is doubtful, though, whether the display would have been enough to have had left-back Paul Konchesky, also watching from the stands, reconsidering whether to complete on his move from Fulham in the next 24 hours.
Four minutes after the interval Steven Gerrard controlled the ball on his chest before attempting a speculative 40-yard volley which dropped harmlessly wide of Carson's left-hand post.
West Brom midfielder was off-target with two long-range efforts while the closest Liverpool came to scoring was when Martin Skrtel hooked a half-cleared Torres cross narrowly wide of the right-hand post.
That was until Baggies defender Jonas Olsson almost gifted them a goal when he attempted to roll Tamas' pass back to Carson but sent it past the far upright.
The goal eventually came in the 65th minute when Torres combined with Dirk Kuyt down the left and when his team-mate returned the ball to the edge of the penalty area the Spain striker expertly shifted his position to volley into the turf and past Carson.
Seven minutes later he almost had his second when he side-footed Gerrard's far-post cross straight at Carson.
Eight minutes from time he was denied again when Kuyt and Gerrard worked the ball across the top of the penalty area only for the Spaniard's strike to be charged down by Gonzalo Jara with the aid of an arm - unseen by referee Lee Probert.
However, the referee did spot Morrison's lunge at Torres and responded with a straight red card.
Torres departed after another 89-minute work-out safe in the knowledge he is gradually edging closer to his prolific best and Liverpool had secured their 2000th league victory.