Christian Eriksen scored the third quickest goal in Premier League history after just 11 seconds which instantly signalled defeat for the Red Devils.
Phil Jones hit a beauty of a strike into the net on 28 minutes, just into the wrong one, to double the hosts' lead and seemingly kill José Mourinho's men off completely.
The result means United are still second in the league, but the gap between them and outside the top four has been cut to five points so an instant bounce-back is crucial.
Expect a Shaw recall on Saturday
David de Gea - 5: The Spaniard didn't look comfortable all night, and you can't blame him considering how the four men in front of him were playing, but couldn't do anything about the two goals.
Antonio Valencia - 4: He failed to contribute to United's rare attacks whatsoever and Son Heung-min was running circles around Valencia, who is normally very sound defensively, all night.
Chris Smalling - 3: Based on that awkward showing it's fair to say the sooner Eric Bailly returns, the better. Spurs profited off his awkwardness all night and he looked lost for their early first goal.
Phil Jones - 4: The comical own-goal for 2-0 can't be ignored but his usual trenchant tackles and interceptions were there at times - he was certainly the stronger of the two centre-halves that's for sure.
Ashley Young - 3: It wouldn't be surprising if Luke Shaw, undeservedly dropped in the first place, return against Huddersfield Town after what was, without question, Young's worst showing of the season.
Nemanja Matić - 2: He's been rather uninspiring for weeks now, and Matić once again failed to fulfil his role correctly as he was dominated by the energetic nature of Dele Alli - needs to dramatically improve.
Mourinho gives Pogba a reality check
Paul Pogba - 3: José Mourinho was expressing his frustration with the side all night long and had a disagreement over tactics with Pogba on the touchline in the second half.
Another poor showing in a big game from the Frenchman and was rightly brought off the pitch moments after his hard discussion with the Portuguese boss - for the first time without an injury.
Alexis Sánchez - 5: The players around Sánchez didn't impress and he was the only attacker who looked interested in making something click in the final third for large parts of the game - isolated for the majority.
Jesse Lingard - 4: 'J-Lingz's' eye-catching Wembley goalscoring record wasn't even almost strengthened and his threat was dealt with admirably throughout the whole game down the middle.
Anthony Martial - 4: Martial was moved to the right to accommodate Sánchez and had a horror-show there. He would've been the one replaced by Marcus Rashford if he came on instead of Herrera.
Romelu Lukaku - 5: The big Belgian was the only United player to really test Hugo Lloris and held the ball up well at times. However, he was still unreliable in possession and was another attacker isolated.
Fellaini substitution mishap sums up night
Juan Mata - 3: No impact, at all.
Marouane Fellaini - 2: Replaced Paul Pogba in the 63rd minute, only to be taken off seven minutes later after ignoring his manager's instructions. Mourinho says he's 'injured.'
Ander Herrera - 3: Similarly to Mata, no effect at all when he came on. It should've been Rashford.