United striker Andy Gray and Sunderland defender Gary Breen were sent off in an incident packed game as Paul Shaw grabbed a 67th minute winner to ease United's mini crisis against a Sunderland side with four straight league wins behind them.
The pair were red carded in the 38th minute for fighting in an off the ball incident with the Bramall Lane side carving out the chances.
United almost snatched the lead with just two minutes gone after midfielder Alan Quinn had been upended 20 yards out.
Tommy Black's free-kick was headed on by Shaw, Stephen Wright moved in to intercept and instead steered the ball towards his own goal before Mart Poom pulled off a stunning save to deflect it round the post.
Top scorer Gray dragged a low shot wide after neat work from Leigh Bromby before Jeff Whitley let fly from the edge of the area, his stinging shot tipped over by Paddy Kenny.
Former Sheffield Wednesday defender Bromby sneaked forward in the 17th minute to unleash a volley palmed over by Poom. The Sunderland keeper pulled off an even better stop minutes later deflecting Shaw's angled drive from 25 yards.
United suffered a blow in the 30th minute when skipper Chris Morgan limped off to be replaced by former Middlesbrough defender Alan Wright before both sides were reduced to ten men.
Poom foiled the Sheffield side again seconds from half-time, stretching to punch Jon Harley's eye catching 25 yard shot over the bar.
Midfielder Darren Carter fired over the top and Poom produced another stop diving to divert Alan Quinn's close-range shot after the former Sheffield Wednesday midfielder had weaved into the box.
United snatched the lead after Dean Whitehead 's poor back pass to Steve Caldwell was cut out by Shaw, back at the club because of injuries to three strikers, who nipped in to stab the ball to the left of the helpless Poom.
Substitute Jonathan Forte almost added a second eight minutes from time ending a dazzling run with a ferocious shot from 20 yards which crashed against the post.