Bruno Fernandes opened the scoring from the penalty spot after the video assistant referee spotted a Will Hughes handball and United seemed to be cruising when Rashford turned home Luke Shaw’s cross 17 minutes into the second half for his 11th goal since returning from Qatar.
But the contest turned dramatically when, amid a confrontation that resulted in both Antony and Jeffrey Schlupp being booked, VAR Tony Harrington spotted Casemiro with his hands round Hughes’ neck.
After a pitchside review, referee Andre Marriner sent the influential Brazilian off for violent conduct, which triggers an immediate three-match domestic ban.
Follow Saturday’s Premier League action
How did you rate Manchester United’s performance? Have your say here
What did you make of Crystal Palace’s display? Send us your views here
Schlupp halved the deficit almost immediately and amid increasingly frantic scenes around the home area, United ended the game with four central defenders protecting their goal as Harry Maguire and Victor Lindelof were added to starting pair Lisandro Martinez and Raphael Varane.
Respective managers Erik ten Hag and Patrick Vieira, who started the afternoon laying wreaths in honour of the victims of the 1958 Munich air disaster, ended it ranting at fourth official Joshua Smith and then marching to the centre circle to make their points to Marriner as both argued against decisions that went against their team.
United’s 13th consecutive win at Old Trafford lifts them to third in the table while Palace remain 12th.
Rashford and Fred key for United
With Antony Martial ruled out through injury, Rashford’s goals output is going to be crucial for United.
He now has 19 in all competitions and the England man also claimed an assist for the hosts’ opener when his cross was handled by Hughes and Fernandes converted the resulting penalty.
If Rashford’s goals are needed, and with Casemiro now missing two Premier League games within five days against Leeds and the home encounter with Leicester on 19 February, Fred is almost as important.
Manchester United’s Marcus Rashford celebrates after scoring against Crystal Palace
Marcus Rashford scored his sixth goal in seven Premier League games
The Brazilian has tended to be held up as an example of United’s profligacy in the transfer market.
He cost £47m in 2018 but has rarely shown anything positive beyond running around furiously to no great end product.
Yet, as Ten Hag pointed out recently, the midfielder partners Casemiro for his country “and Brazil are not a bad side”, suggesting the 29-year-old is capable of more than he has produced in his nearly five seasons in the Premier League.
He has looked a different player in recent times.
Fred still hustles and harries but he also links play well, is prepared to shoot from distance and, as he proved when he burst into the box and sent Wout Weghorst’s cut-back to the near post narrowly wide of the Palace goal, can be a significant threat inside the area as well.
When he laid on his back deep in injury time and gulped in some air, it underlined the effort Fred had put in during the desperate defending United were forced into at the end.
Palace poor run continues
This was yet another day when Palace played well and ended without reward.
Vieira’s side now have five points from their past eight games, form that must be overturned if they are to stay out of trouble at the bottom of the table.
Schlupp was excellent. His goal was instinctive and he also created an opening in the first half with a neat turn into space.
The absence of Wilfried Zaha with a hamstring injury was not a major blow in that sense and it took a brilliant David de Gea save to deny skipper Marc Guehi and concede the corner from which Palace scored.
However, while they are unquestionably a better side to watch than in Roy Hodgson’s day, they are also easier to score against.
They have only five top-flight clean sheets all season and the room Rashford was afforded for what turned out to be the winner was poor considering how close he was to goal. Amid the fluidity of his side further forward, Vieira must not neglect the basic art of defending.