Southampton youngster Alex Jankewitz lasted just 79 seconds on his first Premier League start as the defender was sent off for a reckless lunge before Manchester United went on to put nine past them in an embarrassing defeat.
Ralph Hasenhuttl had handed the 19-year-old his debut against Aston Villa on Saturday as an 89th-minute substitute and started him here, but Jankewitz was given his marching orders early on for a horror challenge on Scott McTominay.
Jankewitz's moment of madness set the tone for the rest of the match and United punished the ill-discipline of the visitors, who finished with just nine players.
The game was as good as over by half-time as United went in four up thanks to goals from Aaron Wan-Bisakka, Marcus Rashford, Edinson Cavani and a Jan Bednarek own goal.
And things went from bad to worse for Southampton with Martial and McTominay making it six before they were reduced to nine men with Bedranek dismissed late on.
United added gloss to the scoreline as Bruno Fernandes, Martial and Dan James all scored in the final few minutes to complete the rout.
Rio Ferdinand criticised Jankewitz for putting the Saints in the lurch after seeing red for his 'terrible tackle'.
'It was a crazy tackle to start the game off,' the ex-United man told BT Sport.
'It killed everything we thought was going to happen in the game.
'From that moment on it was only a red shirt who was going to get the ball in the back of the net. Such a bad tackle.
'When I saw it the first time I thought it was bad but when you see it here close up it’s a terrible tackle. I don’t think the manager will need to get into him at half time, he’ll know.'