What you need to know:
- United have now lost four of their opening six games of the season for the first time in 37 years.
Manchester United goalkeeper Andre Onana said he had let his teammates down after a howler set the tone for a 4-3 Champions League defeat to Bayern Munich.
A third consecutive defeat ramps up the pressure on United manager Erik ten Hag and two late goals from Casemiro masked the gulf in class between the sides at the Allianz Arena on Wednesday.
However, United had started brightly until Leroy Sane's strike slipped through Onana's grasp on 28 minutes.
"After my mistake we lost control of the game. It's a difficult situation for us, for me especially because I'm the one who let the team down," Onana told TNT Sports.
The Cameroonian starred for Inter Milan on their run to last season's Champions League final, but has struggled in the early weeks of his United career since joining in a £47 million ($58 million) move.
The Red Devils have now conceded three or more goals in three consecutive games for the first time since 1978.
"My start in Manchester is not so good, it's not how I want (to play)," added Onana.
"Today is one of my worst games and it is difficult because we have big ambition, we want to win everything - it was a big opportunity for us to bounce back after the situation we are facing.
"It's a tough time. We have to be together and learn from our mistakes because it's the only thing to do."
United have now lost four of their opening six games of the season for the first time in 37 years.
Ten Hag earned plenty of plaudits for his first season in charge as he led United back into the Champions League and ended a six-year trophy drought by lifting the League Cup.
But his side's downward curve dates back to the latter part of last season. Since a historic 7-0 humiliation at the hands of Liverpool in March, United have lost eight of their last 12 games away from home in all competitions.
Ten Hag called for character from his side to bounce back from being outplayed on home soil by Brighton 3-1 at the weekend.
Instead, the former Ajax boss will be concerned at how quickly his side crumbled after Onana's blunder and twice conceded within seconds of getting back into the game.
Serge Gnabry quickly doubled Bayern's advantage after Jamal Musiala burst through the United defence with ease.
Rasmus Hojlund's first goal for the club was the big positive of the night for Ten Hag's men.
But Harry Kane had restored Bayern's two-goal cushion within five minutes from the penalty spot after Cristian Eriksen was harshly penalised for handball.
Bayern should have then ran up a far more convincing scoreline as they twice hit the woodwork and eased up by bringing off Kane, Sane, Gnabry and Musiala.
Casemiro's first goal could have provoked a nervy finale had Mathys Tel not been given space to crash in Bayern's fourth within three minutes.
The Brazilian then headed in his second with virtually the last action of the match.
"When you score three goals at Bayern then you have to at least take a point," said Ten Hag.
But he was keen to point to a collective failure rather than pointing the blame at Onana.
"If you see the first 25 minutes you have to score, but if not stay in the game. Don't allow the opponent to score goals like we did. It's not only about one mistake."