Interim boss Darren Fletcher, still searching for his first win after Ruben Amorim's sacking, watched his side crumble against a clinical Brighton side that exposed yet more defensive frailties. Former United forward Danny Welbeck stole the show, assisting the opener and scoring a stunning second against his old club, ensuring Brighton's historic first FA Cup victory over the 13-time winners at the seventh attempt.
The misery started early. Just 12 minutes in, Welbeck delivered a precise cross from the left, Georginio Rutter nodded it goalwards, and goalkeeper Senne Lammens could only parry into the path of Brajan Gruda, who rifled home the rebound to give the Seagulls a shock lead.
United dominated possession and created chances—Kobbie Mainoo was particularly bright in midfield, crafting several openings—but lacked the killer instinct. Brighton, refreshed after a midweek draw at Manchester City, defended resolutely and struck decisively on the counter.
The killer blow came in the 64th minute. Welbeck ghosted in behind the defense, received a pass from Gruda, and curled a magnificent effort into the top corner with the outside of his boot—his second goal against United this season after scoring in the earlier Premier League clash.
A late lifeline arrived in the 85th minute when Benjamin Sesko powered home a header from a Bruno Fernandes corner, sparking brief hope among the frustrated Old Trafford crowd. But any momentum was snuffed out when substitute Shea Lacey—the 18-year-old academy prospect—was sent off in the 89th minute for a second yellow card (dissent following a late tackle).
Brighton held firm through added time, securing a deserved victory and dumping United out of the competition. The result leaves the Red Devils with just the Premier League to fight for this season—their lowest number of competitive games (around 40) in over a century—and heaps more pressure on the club's hierarchy as they hunt for a permanent manager.
Fletcher, whose interim stint now reads winless, admitted post-match: "We created enough to win but didn't take our chances. Disappointed, but we must regroup for the derby." Meanwhile, Brighton's Fabian Hürzeler praised his side's ruthlessness and depth, with Welbeck captaining the team in a rotated lineup.
This defeat deepens United's woes: booing at full-time, a trophyless campaign looming, and questions mounting over the direction of the club. Brighton advance to the fourth round, while United turn their focus to the Manchester derby against City on January 17—another must-win in a season fast becoming a nightmare.
A day Old Trafford would rather forget, but one that highlights the gulf between ambition and reality at the Theatre of Dreams.