Despite having 21 goals to his name this season, Bent only appears to have an outside chance of being part of Fabio Capello's England squad in South Africa, but even though he will probably be deemed surplus to requirements this summer he remains vitally important to Sunderland who took another huge step towards mid-table safety thanks to his endeavours.
Bent proved his worth to Sunderland by striking two early goals, as Birmingham City got off to an appalling start, before the visitors dominated proceedings.
Ultimately, though, they only had Cameron Jerome's second-half goal to show for their efforts as inspired Sunderland goalkeeper Craig Gordon pulled off a string of saves, as brilliant chances came and went on a regular basis, before Fraizer Campbell scored late on to put the points beyond doubt.
Bent showed how it should be done to put former Birmingham manager Steve Bruce's side on course for victory in the fifth minute with his 20th goal since leaving Tottenham last summer.
Fewer goals could have been simpler as he just had to take a touch before swinging his left foot at the ball, when Benjani's shot ricocheted into his path off Stephen Carr, to beat Joe Hart from close range.
Bent doubled the lead six minutes later when he found space just inside the penalty area and was picked out by the revitalised Steed Malbranque and took a touch before striking another left-footed shot beyond Hart.
Fraizer Campbell almost extended Sunderland's lead five minutes later when he managed to unleash a shot, despite the attentions of three Birmingham defenders, but his effort cannoned off Hart.
Sunderland's dominance was down to their midfield superiority where Michel Madera, surprisingly handed a starting berth ahead of Lee Bowyer, looked out of his depth against David Meyler and Kieran Richardson.
Jerome led Birmingham's resistance with a powerful run down the left wing that saw Keith Fahey test Gordon with a 20-yarder that the Scotland international pushed away.
Birmingham, who pulled back two goals to draw 2-2 against Everton last weekend, raised their collective game after that shambolic start and Gordon denied Fahey before brilliantly pushing away Christian Benitez's header following Carr's cross.
Birmingham's threat faded and Richardson underlined his return to form when he beat a couple of Birmingham defenders on the edge of the box before curling a shot towards Hart's top-right hand corner, but the goalkeeper flung himself across the goal to repel the stinging effort.
Sunderland ended the first half on the back foot and Jerome was unable to convert a difficult chance following Liam Ridgewell's cross.
Jerome should have reduced the deficit after the break, when he was sent clear by Michel, but Gordon saved with his feet to leave Alex McLeish exasperated as the striker put precision over power.
Gordon then pulled off two excellent saves to deny Benitez and Carr as Birmingham pressure intensified.
McLeish sent former Sunderland striker Kevin Phillips and James McFadden on in place of Benitez and Fahey respectively on the hour and within seconds his team hit back.
Again the increasingly influential Michel put Jerome through and this time the former Cardiff player finished confidently, finally finding a way past Gordon when he curled in a delightful shot.
That proved to be a false dawn for Birmingham for, despite dominating, Gordon remained imperious as he pushed away Ridgewell's header before Roger Johnson nodded over McFadden's corner.
Sunderland struggled to get out of their own half and Bent could only head Richardson's cross straight at Hart, missing the chance to give his defensive colleagues much needed breathing space.
Scott Dann denied Bent a hat-trick late on when the forward lobbed Hart only to see the centre-half clear off the line in a nerve-jangling finale.
Campbell settled local nerves in the 89th minute when he pounced to slide Jordon Henderson's excellent low cross past Hart.
Gordon wasn't finished, though, and somehow kept out Gardner's header with a stoppage-time block.