Published: 2017-04-17 00:25:12 BdST
Goals by Marcus Rashford and Ander Herrera sank Chelsea and, with six games left for the top two, there is little room for any more slip-ups by Antonio Conte's side who a few weeks ago looked like they were running away with the title.
While Chelsea remain favourites to win the league, Conte will be concerned about the manner of the defeat at Old Trafford where they were rarely able to turn possession into chances.
The west London side are top with 75 points ahead of Spurs on 71, also from 32 games, Liverpool with 66 from 33, Manchester City on 64 from 32 and United with 60 from 31.
The strikes by Rashford and Herrera at the start of each half were enough for United who, despite resting several players against Chelsea ahead of Thursday's Europa League quarter-final return leg at home to Anderlecht, were good value for their win.
United manager Jose Mourinho started with top scorer Zlatan Ibrahimovic on the bench but delivered a tactical masterclass against his former club, largely nullifying the threat from the usually dangerous Eden Hazard.
Chelsea got a warning after five minutes when United forward Jesse Lingaard robbed defender David Luiz and fed Rashford, but the 19-year-old striker dragged his shot wide.
Two minutes later, though, Herrera won the ball in midfield, possibly by using his hand, and delivered an inch perfect pass into the path of Rashford, who outpaced Luiz and fired low into the far corner of the net.
Looking confident and full of verve, United pushed forward with intent while Chelsea were unusually ineffective going forward, with Herrera doing an excellent marking job on Hazard.
There was another individual battle going on with Chelsea striker Diego Costa and United defender Marcos Rojo engaged in an often physical struggle for dominance and Costa’s frustration resulted in a yellow card for a foul on Paul Pogba.
United threatened to strike again before the break when Rashford found some space for a cross which Chelsea defender Gary Cahill headed just over his own bar.
United's Ashley Young then blasted over from a promising position on the stroke of halftime but the hosts did not have to wait long after the break to double their advantage.
Chelsea's normally reliable N’Golo Kante was robbed inside the area by Young and he cleverly laid the ball back to Herrera whose well-struck effort deflected off Kurt Zouma into the net.
Ibrahimovic was brought on for Rashford in the 82nd minute, with the England striker receiving a deserved standing ovation after an outstanding performance.
While United’s hopes of making the top four will be boosted by the win, the major impact will be felt in north London where Spurs will sense a chance to chase down Chelsea’s four-point lead in the final six games of the season.