Harry Kane scored his first Champions League goal for Bayern Munich as they beat a depleted Manchester United 4-3 in their Group A opener, with three goals in the final six minutes.
The build-up to a famous European tie had focused on Kane's past transfer links to Man Utd, although the England captain maintained Bayern was always the right destination for him after leaving Tottenham.
But there was still a sliver of irony as he dispatched from the penalty spot for his first Champions League goal for the German side, given after a chaotic and controversial VAR review for a Christian Eriksen handball.
It came shortly after Rasmus Hojlund's first Manchester United goal (49), which was taken well by the 20-year-old on his own European debut for his new club.
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The game looked to be heading towards a comfortable 3-1 win for Bayern, but a topsy turvy final six minutes showed Man Utd have some fight left in them yet. Casemiro (88, 90+5) scored twice, either side of a Mathys Tel fourth for the hosts.
The signs of life will be welcome after - as has often been the case this season - Man Utd created their own problems in defence in the first half. They have now have conceded three or more goals in three consecutive games in all competitions for the first time since December 1978.
It was an Andre Onana howler that saw Leroy Sane (28) open for Bayern, before a fine Serge Gnabry (32) finish doubled the hosts' lead.
In an honest interview with TNT Sport, Onana owned up to his mistake, saying: "The team was really good but it was because of me we didn't win this game.
"I have a lot to prove. My start in Manchester has not been good or how I want. The way I played today was one of my worst games.
"It's difficult as we are a big club who wants to win everything. It was a good opportunity to bounce back after the situation we are facing - it's a tough time, we have to be together and continue to work hard."
The Bundesliga champions go top of Group A after Galatasaray and Copenhagen drew 2-2 earlier on Wednesday. Man Utd sit bottom of the group after one game.
How Bayern beat Man Utd in Champions League opener
Manchester United began well at the Allianz Arena. They should have gone ahead inside four minutes when Eriksen sent a fine ball through the six-yard box. But a well-timed tackle from Alphonso Davis stopped Facundo Pellistri from striking, before Eriksen's follow-up was saved by Sven Ulreich.
Man Utd continued to make life difficult for Bayern, but a poor error from Onana saw the hosts ahead. A threaded ball from Kane found Sane, whose low shot - speculative at best - managed to squirm underneath the goalkeeper's body and into the back of the net.
Unsurprisingly, a second followed five minutes later. It was sublime play from Jamal Musiala to surge into the box. He then pulled the goal back for a waiting Gnabry, who slotted home into the far corner.
Although Man Utd offered little by way of response in the first half, they hit back four minutes after the break to give themselves a lifeline. Marcus Rashford tapped the ball into Hojlund's path, and it was a neat finish from the forward into the far corner.
But Man Utd were dealt another harsh hand after Bayern were awarded a penalty soon after. Initially, it appeared as if VAR had dismissed the claims after Dayot Upamecano's cross hit Eriksen on the top of the arm.
However, VAR took another look at the incident, eventually sending the referee over to the screen. The penalty was then awarded - to a shake of the head from Erik ten Hag - as Kane expertly dispatched past Onana for his first Champions League goal for Bayern Munich.
Bayern continued to press for another - Sane hitting the post before the Man Utd goalkeeper redeemed himself with a string of saves to deny the likes of Musiala and Eric Maxim Choupo-Moting.
But there was drama to come and it began as Casemiro squeezed home Man Utd's second in the 88th minute. He was picked out by Anthony Martial and despite ending up on the floor when his first effort was blocked, managed to sweep the ball home with his foot.
Bayern gave Man Utd a lesson throughout on how to respond to goals, and added their fourth in the second of four added minutes - coming after Thomas Muller had hit the post. But it was a fine finish from Tel, that was expected to be the final goal of the game.
But Casemiro had one final word with the last kick. He nodded home from a Bruno Fernandes set-piece, but despite the momentum, there was no time left for an equaliser.
Ten Hag: Sane went through too easily
Man Utd manager Erik ten Hag:
"I'm disappointed as we should have stayed in the game. When you score three goals at Bayern you should at least take a point.
"We are in a period where a lot is going against us but we have to make our own luck. When you don't stick the rules or principles of our game you concede goals but we have played three great teams in the last three games.
"It's good he's doing that [Onana owning his mistake] but it's about the team. Mistakes can be made but you need to bounce back as a team. When you score three goals and one player makes a mistake, it's gone.
"We have to believe we can bounce back, tonight we showed it. You have to stay in the game and keep going despite mistakes.
"For the first 25 minutes, we were better than Munich. Then, that goal was so easy. It's not only Andre, if you see how easy Sane is coming through and that has to do with determination. You don't let players so easily through. That's the point we have to cross the line as undefeatable and as a team to win games because it started there.
"Every game is important. Every game is huge. No-one can help you. If you see the first 25 minutes, you have to score but if not, stay in the game and don't allow the opponents to score a goal like we did.
"It's not only about that mistake as even before that it was too easy for the player to have a shot. You have to be consistent in such moments then you will win games.
Kane: We're one of the CL favourites
Harry Kane speaking to TNT Sports:
"It was a crazy finish but for the majority we controlled it, dictated the tempo and we lost concentration in the last five minutes. Overall, it was a really good start against a tough side.
"It's always great to score but there's a room for improvement.
"As a striker I know I'm going to get chances, it's exciting to play with them [creative players] but we're still getting to know each other. It's exciting what is to come, if we're doing what we're doing now and add the understanding, then it's really exciting.
"When there is a big price tag there is always expectation and you want to repay the club for the faith. It's been a really good start. We're one of the favourites but first of all we need to get the job done in the group and then hopefully look forward to the knockout games.
"They [Man Utd] are going through a difficult spell and suffering with injuries. They have a lot of talent, they can score and turn games around really quickly. I'm not too worried about them, I'm focused on myself. I'm sure they'll improve and get back to their best but I'm just concentrating on us and I'm enjoying it so far."
Bayern manager Thomas Tuchel on Kane: "We played him in a different role in a half position today to turn and to assist to our speed on the sides.
"We found him more involved in the second half, like most of the team. He was more fluid, we found him better in the half spaces, they opened up minute-by-minute.
"Then he had some chances that he took, which is fair enough as a No9. He scored a very important penalty to have a two goal lead again after just conceding so everything is fine."
Opta stats - Sane scores again vs Man Utd
- Manchester United have lost three consecutive matches within a single season in all competitions for the first time since April 2019 under Ole Gunnar Solskjaer.
- Bayern Munich have won their opening UEFA Champions League match in each of their last 20 participations - no other club has done so in more than 12 consecutive appearances in the competition.
- Manchester United have conceded 14 goals in all competitions this season, the most of any Premier League side.
- Leroy Sane has scored in consecutive appearances against Manchester United, also scoring against them for Manchester City in April 2019. Sane has now been directly involved 20 goals in his last 18 home matches in the UEFA Champions League (12 goals, 8 assists).
What's next?
Manchester United look to kick-start their Premier League season at Burnley on Saturday night. Kick-off 8pm. United play Galatasaray in their next Champions League Group A fixture on Tuesday October 3. Kick-off 8pm.
Bayern Munich host VfL Bochum in the Bundesliga on Saturday at 2.30pm. Their next Champions League fixture sees them visit Copenhagen on October 3. Kick-off 8pm.