Ole Gunnar Solskjaer expects Marcus Rashford to be out for a “little while” with his groin problem.
Rashford, who had played against Astana in the Europa League in midweek, was particularly sluggish before being withdrawn.
His exit left United without a recognised striker as Jesse Lingard was forced to lead the line.
And Solskjaer confirmed afterwards that United would be without their main striker for some time.
Solskjaer confirmed Rashford would undergo a scan on his groin injury on Monday.
The United boss conceded the striker would be out “for a little while”.
United were already without Mason Greenwood and Anthony Martial for the clash at the London Stadium.
Greenwood, who scored the winner against Astana, was missing through tonsilitis.
Martial also sustained an injury in the defeat to Crystal Palace but both could be involved against Rochdale in the Carabao Cup in midweek.
Solskjaer also confirmed Paul Pogba was expected to play in that encounter against the League One side.