It was a performance that saw the bones of Ole Gunnar Solskjaer's squad laid bare in brutal fashion, as the Red Devils finished the first half down 4-1.
Despite an early Bruno Fernandes penalty handing the hosts the perfect start inside the first 120 seconds, the Red Devils subsequently saw the tables turned on them as former United manager Jose Mourinho saw his Spurs side run rampant against a slipshod United defence.
Harry Maguire and Eric Bailly were frequently at fault around the back, with the former particularly responsible for the visitors' first goal as he opted to head a dangerous ball around his own box, before falling over team-mate Luke Shaw to allow Tanguy Ndombele to smash home from close range.
Spurs doubled their haul in quick succession after Maguire brought down Harry Kane in midfield - and the England skipper outfoxed his international team-mate with a quick low free kick into the space where he and Bailly should have been, allowing Son Heung-min to latch on and clip home past David de Gea.
The South Korea international turned provider for Tottenham's third just beyond the half-hour mark, only moments after United were reduced to 10 men with Anthony Martial sent off for a tapping his hand in Erik Lamela's face after the latter appeared to elbow him.
Son played his part in a fine one-two after Kane dislodged Nemanja Matic of possession around the United box, following De Gea and Bailly's decision to play out from the back, with the England man clipping it past the keeper.
And it was the former again who compounded United's misery by doubling his tally with a shot through De Gea's legs following a lovely ball from Serge Aurier.
The deficit represented the Red Devils' worst performance in the opening half of a match in the Premier League era - and raised serious questions about their squad's ability to challenge this term.
Social media didn't hold back at the horror-show on display either, with many weighing in on a historically bad day for United.
I mean, United are the architects of their own downfall here but how that's a red for Martial and not for Lamela WITH VAR is beyond me— Si Lloyd (@SmnLlyd5) October 4, 2020
Just the £245million spent on that Man Utd back six— James Benge (@jamesbenge) October 4, 2020
A disasterclass of defending from Man Utd today. 4-1 down and not even half-time..— Mark Ogden (@MarkOgden_) October 4, 2020
A very bold move by Solskjaer to play Luke Shaw at centre-back and defensive midfield, leaving the left side of their defence completely open. For some reason it's not working— JJ Bull (@jj_bull) October 4, 2020
1% of the PL goals Man Utd have ever conceded at Old Trafford have come in the first 37 minutes of today's game— Duncan Alexander (@oilysailor) October 4, 2020
Maguire needs another emotional BBC interview to explain his actions pic.twitter.com/XbjmMeHM5p— FootballJOE (@FootballJOE) October 4, 2020
It’s not quite Kepa Arrizabalaga territory, but £80m for Harry Maguire is aging like unpasteurized milk.— Zach Lowy (@ZachLowy) October 4, 2020