The Red Devils were among 12 clubs that last month signed up for the breakaway European Super League, which collapsed within 48 hours due to huge, unrelenting pressure.
Those plans brought anger against the already despised Glazer family to a new level, with fans congregating at Old Trafford to demand change ahead of Sunday’s Premier League match against rivals Liverpool.
But hundreds of supporters got into the stadium and on to the pitch, leading to an initial unspecified delay to the 4:30pm BST kick-off.
The Premier League said that “the safety of everyone at Old Trafford is paramount” and confirmation came through from United at 5:30pm that the match had been postponed.
“Following discussion between the Police, the Premier League, Trafford Council and the clubs, our match against Liverpool has been postponed due to safety and security considerations around the protest today,” a club statement read.
So, what happens next?
When will Man Utd play Liverpool?
United and Liverpool both confirmed that discussions will take place to find a revised date for the game, but the run-in is tight - particularly with United set to play the second leg of their Europa League semi-final against AS Roma in Rome on Thursday night.
Monday and Tuesday were theoretically free, but with the likelihood of further protests a possibility, the game was not played on either date - and that makes things more difficult.
Both teams must play their final games of the season on May 23 at 4pm, with that kick-off time set in stone with the rest of the top-flight fixtures that day.
United and Liverpool are also both in action on May 19, and games on 8th/9th May respectively make those dates difficult.
Realistically, without moving other fixtures or playing a day before/after another games, two dates - Friday, May 14 and Friday, May 21 - stand out given both sides have a free day either side of those dates.
Man Utd fixtures
May 6 | Roma (a)
May 9 | Aston Villa (a)
May 12 | Leicester (h)
May 19 | Fulham (h)
May 23 | Wolves (a)
May 8 | Southampton (h)
May 16 | West Brom (a)
May 19 | Burnley (a)
May 23 | Crystal Palace (h)