Manchester United players reportedly were found high-fiving each other in the dressing room despite losing a crunch Champions League match last year.
The Red Devils crashed out in the Champions League group stages in one of the low points of Erik ten Hag's reign as manager, which was ended on Monday.
Ten Hag's side earned just four points from their six matches to finish bottom of the group behind Bayern Munich, FC Copenhagen and Galatasaray.
Their miserable campaign began with a 4-3 defeat by Bayern Munich, with the German giants storming into a 2-0 lead through Leroy Sane and Serge Gnabry.
Sane’s opener had come as a result of a disastrous error from goalkeeper Andre Onana.
Harry Kane and Mathys Tel also scored for the hosts on the night, who also struck the post on two occasions.
A Rasmus Hojlund strike and two late goals from Casemiro gave the score a more respectable look for Man United.
According to The Times, the reaction of Man United's players to the defeat 'rang alarm bells' for Ten Hag and his staff.
Man United stars had reportedly been seen high-fiving each other in the dressing room after the defeat and congratulating the team on their performance at the Allianz Arena.
Staff were said to have been left 'rubbing their eyes' after witnessing the reaction from players.
The result had continued a nightmare start to Man United's season, with the loss coming off the back of three defeats in the club's first five Premier League matches of the season.
Man United ultimately crashed out of Europe and endured their worst finish of the Premier League era, with Ten Hag's side finishing eighth.
The Red Devils, however, earned a shock win over Man City in the FA Cup final which contributed to Ten Hag's contract being extended.
The Dutchman's spell as Man United boss was ended on Monday with Ineos sacking him nine matches into the Premier League season, with the club languishing in 14th in the table and without a win in Europe for a year.
Ten Hag, who will receive a £15million payout, has reportedly been left 'completely devastated' by his dismissal.
Sporting Lisbon boss Ruben Amorim is expected to be confirmed as Ten Hag's successor.
He is expected to stay in charge of the Portuguese club for another three games – including the Champions League clash with Manchester City on Tuesday.
Amorim vowed to end the uncertainty over his future after Friday's game against Estrela da Amadora, hinting heavily that he wants to prove himself in the Premier League.
The 39-year-old will be the latest boss tasked with getting a tune out of the Man United dressing room.
