Watch: Howler from contrite Onana costs Man United in loss to Bayern

Manchester United avoided getting embarrassed in Germany after some shaky goalkeeping in their opening Champions League game, losing 4-3 against Bayern Munich on Wednesday.

After a promising opening to the game, the wheels started to fall off for Manchester United after Leroy Sane's shot in the 28th minute slipped through Andre Onana's hands to give the hosts a first-half lead.

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"We started very good. After my mistake, we lost control of the game. It's a difficult situation for us, for me," Onana told TNT Sports post-match, according to BBC Sport.

The blunder was the latest blemish this season for the Cameroonian goalkeeper, who has struggled since joining Manchester United from Inter Milan.

"I have a lot to prove. My start in Manchester hasn't been so good, not how I want. This was one of my worst games," Onana said.

"It's a tough time. We have to be together and work hard," he added.

Bayern Munich doubled their lead shortly after the opening goal when Serge Gnabry beat Onana from inside the penalty area in the 32nd minute.

In the second half, Rasmus Hojlund scored his first Manchester United goal before Harry Kane converted a penalty to restore Bayern's two-goal advantage. Then Bayern Munich wiped out another United comeback bid after Casemiro's strike was canceled out by Mathys Tel's goal.

Onana has now conceded 14 goals in six games in all competitions.