Casemiro's mindless red card turned a routine victory into a nail-biting finale as Man Utd held on to beat Crystal Palace 2-1 at Old Trafford.
Before the Brazilian was dismissed by a VAR review for putting his hands around Will Hughes' neck, United appeared to be in cruise control and led 2-0 through an early Bruno Fernandes penalty and Marcus Rashford's smart finish.
But after they were reduced to 10 men and Jeffrey Schlupp's snapshot gave Palace hope of a comeback, they crumbled and almost threw away victory in the final minutes.
Jean-Philippe Mateta and Eberiche Eze both went close to stretching Palace's unbeaten record against United to three games, but United weathered the storm to limp over the line to a 13th consecutive home victory.
How Man Utd kept up winning home run - just
Man Utd's long winning streak at Old Trafford harks back to the era of Patrick Vieira's playing career - and the visiting manager was as aware as anyone of the dangers posed by an in-form home side.
With that in mind, VAR alerting Marriner to an accidental but blatant Hughes handball barely five minutes in, with Fernandes then sending Guaita the wrong way from 12 yards, was about as far as possible from the opening he wanted from his side.
Things did get better for the Eagles but only once they had survived a number of waves of United pressure. Wout Weghorst's header from a corner forced a strong one-handed stop from Guaita, and Fred was inches away from beating the Spaniard at his near post.
Palace were wasteful with the ball when they did have it and could only muster a 25-yard drive from Schlupp in the first half. They re-emerged with renewed vigour and enjoyed a few near misses, but found themselves 2-0 down to the move of the game.
Seven of United's players were involved in the build-up around the edge of the Palace box, before a ball through to Luke Shaw was squared for Rashford to side-foot home.
At that point, it seemed like United were cruising to three points, and they may have done had they kept 11 men on the pitch. But once a VAR review picked up Casemiro's hands around Hughes' neck during a 20-man melee, everything changed.
Odsonne Edouard fired in a warning shot within moments from 20 yards before Marc Guehi headed straight at De Gea from a corner. Moments later they had their foothold, as Schlupp hooked Doucoure's wayward shot past the goalkeeper from close range.
When Eze scuffed a presentable chance wide Ten Hag decided he had seen enough and moved to a back five - subbing off substitute Alejandro Garnacho to end a 28-minute cameo - but Palace still should have levelled.
A cross from the dangerous Michael Olise was half-cleared by De Gea but returned into the area for Mateta, who had to hit the target from six yards but nodded over with the goal gaping.
United held on unscathed through the rest of seven minutes of additional time to secure their longest run of home wins for more than a decade, and leave any problems caused by Casemiro's absence for another day.