The Swedish center back played the entire match. But neither he nor any other United defender was able to prevent Ukrainian Andrij Jarmolenko from starting the goal shooter shortly before halftime in an otherwise tiring first half where none of the team found the right offensive.
Jarmolenko was cool when he got the ball into the opponent's penalty area and shot the ball low out of reach of goalkeeper David de Gea.
Immediately after the break, United's Juan Mata had a golden position to set the receipt goal - but the Spaniard, despite the open goal, did not get the ball into the net.
The next big opportunity got Harry Maguire in a tangled situation after a corner. However, Maguire's shot was saved and some more really hot goal chances did not wash United forward.
Instead, outside linebacker Aaron Cresswell extended West Ham's lead to 2-0 on an unassailable free kick in the right intersection.
The loss was Manchester United's second in six matches in the league and means that the team loses ground against top rivals Liverpool and Manchester City, which are seven and five points ahead of the table respectively (Liverpool with one match less played).