Second-half goals by Grady Diangana, Toni Martinez and Martin Samuelson sank Manchester United's Under-23s as West Ham United triumphed at the Leigh Sports Village.
The first half was a very tight affair with the hosts managing five shots on target, compared to the Hammers' one, as Joe Riley offered a threat and dragged a shot wide following a fabulous solo run. At the other end, Martinez was unable to convert a clear opening with his head at the far post and Sead Haksabanovic was thwarted by home keeper Theo Richardson.
James Wilson hooked a Demi Mitchell cross over the bar but the second half started badly for United, with Ethan Hamilton caught by a poor challenge and left receiving treatment. A neat move led to Riley's fizzing shot being pushed over by Nathan Trott but the mood completely changed soon afterwards.
Mitchell's fine defending conceded a corner, which Diangana converted at the second attempt from close range, after his initial effort was superbly flipped onto the bar by Richardson. Ercolani was then dismissed for a high challenge on Diangana and the Hammers capitalised.
Richardson made a great low save to deny Martinez but had no chance when the striker, who scored a hat-trick in the reverse fixture at the London Stadium, was left unmarked to nod in a cross by the excellent Diangana. Sloppy defending let in Samuelson for a simple third, as he smashed past Richardson from the left-hand side of the box.
Another brilliant stop by Richardson prevented Martinez, who had earlier seen a goal disallowed, from adding a fourth, while a positive note for the Reds was a Reserves debut for Angel Gomes, who came on in the 70th minute. The England Under-17 star can be pleased with his input, despite the result, as he tested Trott with a couple of trademark free-kicks.
United: Richardson; Riley, Ercolani, R. Williams, Mitchell; Redmond, Scott (Gomes 70); Olosunde, Hamilton (Warren 77), Bohui (Boonen 70); Wilson.
Subs not used: M. Johnstone, Buffonge.