Tottenham were helped by some dreadful United defending, as goals from Son-Heung Min, Harry Kane, Tanguy Ndombele and Serge Aurier secured a dominant Old Trafford win.
Both teams were quick out of the blocks, with three goals inside the first 10 minutes.
Bruno Fernandes’ penalty handed United a second minute lead but Ole Gunnar Solskjaer’s side found themselves 2-1 behind in the blink of an eye.
Harry Maguire’s error gifted Ndombele an equaliser before Kane released Son from a quick free kick two minutes later.
With United unable to react, the visitors kept on coming in waves as David De Gea denied Kane and Aurier.
However, United’s problems went from bad to worse on the half hour mark as Anthony Marital was sent off for clashing with Erik Lamela and Kane pounced on another defensive error to make it 3-1.
But despite United looking dead buried before the break, Spurs showed them no mercy, as Son’s clipped home Aurier’s cross.
United tried to reshuffle during the break, but there was no stopping Spurs, as Aurier raced in behind Luke Shaw to make it 5-1.
As the hosts looked to batten hatches down the hatches it could have been a cricket score in the closing stages.
But in the end, Spurs had to settle for six as Kane fired home from the penalty spot.
FULL TIME AT OLD TRAFFORD IT’S MANCHESTER UNITED 1 TOTTENHAM 6