West Ham striker Diafra Sakho is set to be sidelined for three months with a thigh injury.
Sakho suffered the injury against West Brom on Sunday and an examination has confirmed the extent of the problem.
The 25-year-old Senegal international, who has scored five goals in 14 appearances this season, will undergo surgery on Saturday.
Either Andy Carroll or Nikica Jelevic could deputise at Manchester United in the Premier League on Saturday.
Hammers manager Slaven Bilic described the loss of Sakho as a "big blow".
West Ham are already without midfielder Dimitri Payet, who has been ruled out until February with an ankle injury, while striker Enner Valencia is also sidelined by an ankle problem.
"We are not bad in terms of quantity of injuries, but unfortunately they have happened to key players," Bilic added.
"With the three of them it's a massive blow, but it's a good chance for some of the other guys to step in and show their class."