The Red Devils were beaten 2-1 at home by Brighton in the Premier League
Some Manchester United fans suffered a miserable day on and off the pitch on Sunday as fighting broke out among their number in the stands at Old Trafford.
In what was new coach Erik ten Hag's debut in the Premier League, the Red Devils went 2-0 behind to Brighton in the first half on the opening day of the season thanks to a brace from Pascal Gross.
United eventually lost 2-1 after failing to capitalize on an Alexis Mac Allister own goal which had given them hope in the second half.
With stress and tension high across a fan base used to glory, but which has not seen its team lift a piece of silverware in five years, a fight broke out in one of the stands at the 'Theatre of Dreams'.
Videos and photos that have circulated on social media show two men in an heated exchange and pushing one another.
In one snap, one of the men also appears to have his hand around the throat of his rival.
According to the Daily Mail, fans from the section of seating below then had to intervene in an attempt to diffuse the row, and others looked on in horror.
Ahead of the 2-1 defeat where wantaway Cristiano Ronaldo came on in the second half, Erik ten Hag called on United fans to provide the difference in their plight to win a first Premier League title since 2013.
"If we bring commitment then I think they [the fans] will like it and they will bring the fight back," the former Ajax boss remarked.
"The stadium I think is meant to bring fight and co-operation," he added, though his call to arms appears to have been taken too literally by some that failed to keep their passion in check.
With United already off to the worst possible start, the Red Devils next play at Brentford on Saturday where Ronaldo might still warm the bench as communicated by separate comments Ten Hag made once the Brighton line-up was made public.
"Cristiano Ronaldo is working really hard to get in the right fitness levels, it will take time," the already under-pressure coach revealed, as reported by BBC Sport.
"He started pre-season last week... so it depends on how quick he is progressing," Ten Hag also added, as per when the Portuguese might expect to become a starter again.
According to club legend Wayne Rooney, however, United should cut their losses with Ronaldo and let him leave in order for Ten Hag to build a successful outfit.