Bayern Munich's 3-0 defeat to Manchester City was bad enough, but it has been compounded by claims Sadio Mane left team-mate Leroy Sane with a cut lip after a dressing-room bust-up.

The result in Manchester on Tuesday has left Bayern with a long way to come back in next Wednesday's second leg of the Champions League quarter-final.

Their hopes look bleak, but the on-pitch struggle might just be the beginning of their problems.

Bayern have yet to comment on the claims that came to light on Wednesday, with German newspaper Bild reporting Mane reacted angrily to comments from Sane and lashed out, hitting his team-mate.

There may also be concern within the Bayern ranks about how details of the behind-closed-doors incident leaked out into the media.

For new head coach Thomas Tuchel, the drama was something he could have done without, not least because Mane has already been struggling to live up to his marquee status since arriving from Liverpool.

The Senegalese forward, who joined for an initial €32million last June, sits only sixth on the list of goal involvements for Bayern this season, after managing 11 goals and five assists in 32 games.

Midfielder Jamal Musiala heads that list with 27 involvements (15 goals, 12 assists), and Sane (13 goals, seven assists) is also among those in front of Mane.

The Mane and Sane alleged clash is a topic Bayern will have to address at some point, and that may come on Thursday.

Should it not, coach Tuchel is due to hold a press conference on Friday ahead of the home Bundesliga game against Hoffenheim.

The former Borussia Dortmund, Paris Saint-Germain and Chelsea boss has had a rocky time of it since being appointed successor to the sacked Julian Nagelsmann.

His reign began with a sparkling league win against title rivals Dortmund, but a DFB-Pokal exit followed at the hands of Freiburg, and now hopes of European glory are hanging by a fraying thread.

Bayern CEO Oliver Kahn reacted on Wednesday to the team's bad result at the Etihad Stadium, saying on Twitter: "Even the day after we are still bitterly disappointed. We imagined it differently. But there is still a second leg and I've experienced a lot in football myself."