Manchester United put nine goals past Southampton in a record-equalling Premier League win.
Janowitz was sent off for the visiting side a little over a minute into his debut and United took full advantage through goals from Wan-Bissaka, Rashford, Cavani and a Bednarek own goal before half-time.
United had seven various goalscorers on Tuesday night, only the second time that has happened in a Premier League match after Chelsea pulled off the feat against Aston Villa in December 2012.
Ole Gunnar Solskjaer’s side has now also scored six or more goals in a Premier League match for a second time this season after they defeatgainst Leeds United 6-2 in December. It is the first time they have scored six or more goals in a league game twice since the 2000-01 campaign.
Careful to say Ralph Hasenhuttl won’t be dropping the accusation at Alexandre Jankewitz.
The Southampton boss gave Jankewitz his Premier League debut against Aston Villa on Saturday as an 89th-minute substitute, and his first start at Old Trafford was equally brief.
Only 82 seconds into the game when Scott McTominay blocked Stuart Armstrong’s pass and went into a 50-50 challenge with the Swiss teenager.
For motives best known to him, Jankewitz went over the top and sank his right boot into McTominay’s left thigh.
It was an unbelievably reckless foul and the colour of the card was never in doubt – clearly not with Mike Dean in charge.
Nice or not, the United players didn’t have to pressure the referee on this one.
The stud marks were visible on McTominay’s thigh as he received treatment, and so was the look of utter doubt on Hasenhuttl’s face as Jankewitz made an early exit.
His night was over but Saints knew the punishment was only just the beginning. Plague by injuries, they had arrived here having to close the gaps with academy players like Jankewitz and Kayne Alexandre, who was also making his second league start.
They were four down by half-time and Hassenhuttl must have been worrying a repeat of the 9-0 humiliation he endured at the hands of Leicester City 15 months ago.
For United, it was a pleasant break after a disappointing run that had seen them drop seven points in the event of four games, handing the drive to Manchester City in the title race.
Solskjaer’s side has struggled at Old Trafford this season but unexpectedly this one was there for the taking, and take it they did.
Games like this still need to be won and United was brutal in the way they cut through the nine men.
They took 17 minutes to go ahead when Marcus Rashford played the ball to Luke Shaw who whisked in a cross. Aaron Wan-Bissaka arrived unmarked to meet it the first time, and his shot went in off the far post.
The second goal came in the 25th minute following another good run by Shaw.
He dropped the ball to Mason Greenwood – picked ahead of Paul Pogba– and his pull-back picked out Rashford whose effort crawled past goalkeeper Alex McCarthy.
No-one even assumed a comeback at that stage – presumably even Saints themselves – but a chance arrived when Edinson Cavani needlessly clanged into Moussa Djenepo on the edge of the box. David de Gea was compelled into a terrific save to keep out James Ward-Prowse’s free-kick and his night’s work was just about done.
At least mismatch gave United’s misfiring forwards an opportunity to boost their confidence in front of goal and Cavani, regretful of two glaring misses at Arsenal on Saturday, headed in from Shaw’s inviting cross before half-time.
Solskjaer took the chance to make changes at half-time, sending on Donny van der Beek and Anthony Martial. Dan James followed on soon afterwards.
It was Van der Beek’s foul and yellow card that enabled Ward-Prowse to take a free-kick that broke off with Che Adams scoring at the second attempt.
Adams had a goal ruled out and United then added to their goal tally, with Martial netting twice either side of McTominay’s drive and Fernandes converting a penalty that saw Bednarek red-carded. James completed the scoring in added time.
This win charges United level on points with leaders Manchester City, albeit having played two games more than their bitter rivals.
As for the saints, they are without a point in four Premier League matches and stay in 12th after this historically bad result.