Chelsea crashed to their fifth home defeat of the season - 2-0 to Manchester United as their hold on the coveted fourth spot in the Premier League and thus Champions League next season hangs in the balance.
VAR was the sideshow that seemed to favour the visitors - Chelsea had two goals disallowed by it and it failed to send off Harry Maguire for a kick out on Michy Batshuayi. Maguire scored the vital second goal.
The Blues face Spurs, again at home on Saturday, and another defeat will see the north Londoners leapfrog them in to fourth place.
In truth Chelsea were not good enough.
Injuries prevented Tammy Abraham and Callum Hudson-Odoi from starting, but this was no kids first 11 put out by Frank Lampard and the experienced players failed to perform.
Lampard make a bold call by continuing to drop the world’s most expensive goalkeeper Kepa - thankfully his understudy Willy Caballero did not disgrace himself and was not at fault for either of the two goals.
This was the first time Un tied have done the league double over Chelsea since 1998 - add the Carabao cup defeat and it’s an inglorious treble for the west Londoners.
Both sides started tentatively, but the first effort fell to the home side, Reece James zipping an angled right-footer across David de Gea’s path but the ball inched wide of his right upright on five minutes.
This was quickly followed by Willian trying a left-footer from a similar angle - the result almost the same, except the ball crept over the crossbar.
But there was great disappointment from the home fan after they witnessed midfielder N’Golo Kante’s night ended prematurely as he limped off on 11 minutes with a left leg injury - Mason Mount replaced the World Cup winner.
Quite what VAR’s Christopher Kavanagh deems violent conduct is unclear after Harry Maguire kicked out at Michy Batshuayi on 20 minutes when the United skipper took a tumble in the Chelsea dugout after the two clashed.
Seconds later the striker missed a great chance to open the scoring wen Mount teed up the Belgium hit man - but his left foot drive went wide.
Willian was given a yellow card by referee Anthony Taylor on 36 minutes when Bruno Fernandes appeared to clip the Brazil winger in the United penalty area. But Taylor thought it was a dive instead.
But on the stroke of half-time Wan-Bissaka produced a great 1-2 with Fred and produced a fine right byline cross which Anthony Martial got to ahead of Andreas Christensen. The France striker glanced the ball wide of Caballero to go 1-0 up. Christensen had been nursing a nose injury and could have been distracted by it for the goal. He failed to reappear for the second half, replaced instead by Kurt Zouma.
Chelsea started the second half as if they had had a rollicking from head coach Frank Lampard and Antonio Rudiger smashed home from a Willian corner.
But VAR intervened in favour of the visitors by suggesting that Cesar Azpilicueta has pushed Brandon Williams before the ball fell to the centre-half, the goal was ruled out.
Fernandes crashed a sublime free-kick against the upright on 63 minutes as Chelsea struggled to get a foothold back into the game.
United’s dominance reaped its reward when on 66 minutes Fernandes put in a deep corner and Maguire powered home a thumping header to go 2-0 up.
Lampard decided he needed a change up front - Oliver Giroud came on for misfiring Batshuayi.
Mateo Kovacic took one touch too many in the United penalty are and was foiled by Eric Bailly’s last-ditch interception.
Incredibly a brilliant diving header that zipped into the back of the visitors’ net by Giroud with 13 minutes left on the clock was disallowed by VAR as it was deemed the France striker’s left boot was offside.
A wonderful free-kick by Mount bounded of De Gea’s left post with a min ute to go. But in truth, Chelsea were second best for large sections of the game.
Teams; Chelsea, Caballero, Rudiger, Christensen, Jorginho, kante, Willian, Pedro, Kovacic, Batshuayi, James, Azpilicueta
Subs: Kepa, Alonso, Barkley, Zouma, Giroud, Mount, Tomori
Manchester United: De Gea, Bailly, Maguire, Martial, Fred, Fernandes, James, Shaw, Wan-Bissaka, Matic, Williams,
Subs: Romero, Jones, Mata, Pereira, Dalton, Ighalo, Greenwood
Referee: Anthony Taylor