Benjamin Sesko gave United hope of a fightback by heading home in the 85th minute, but teenager Shea Lacey's sending off four minutes later for throwing the ball into the ground in anger erased all momentum from the goal and United fell out of another cup competition at the first hurdle, meaning their whole season rests on them trying to qualify for Europe. The defeat also severely harms Darren Fletcher's chances of being named interim manager for the rest of the season.
Fletcher swapped out three players from his first game in charge against Burnley on Wednesday, handing Kobbie Mainoo his first start since August while recalling Leny Yoro and Mason Mount to the line-up. Brighton, meanwhile, had made six changes from their 1-1 draw at Manchester City.
United made a very fast start, but after Diogo Dalot squandered a clear one-on-one and skied another effort, the Seagulls took an 11th-minute lead. The goal came from a familiar source, a cross from Welbeck who has a habit of haunting his former club whenever he plays against them, as his cut-back was met by Giorginio Rutter. And although Lisandro Martinez cleared the forward's header off the line, Brajan Gruda turned the rebound in.
United nearly conceded again moments later when Senne Lammens passed the ball straight to Welbeck, but the United goalkeeper managed to get in the way of the shot. Welbeck would not be denied again, though, and scored for the eighth time against United, taking advantage of slack defending from Yoro and Patrick Dorgu to smash into the roof of the net.
Sesko headed United back into the game from Bruno Fernandes' corner, but after a bright cameo, Lacey saw red for two quickfire bookings, and United were unable to create anything else of note in the pursuit of an equaliser.
GOAL rates United's players from Old Trafford...
