Manchester United veteran Victor Lindelof is set for a prolonged spell on the sidelines.
The centre half, who has played more games than expected so far this season, will be absent for a lengthy period.
Lindelof has undergone surgery on an unspecified problem that had to be corrected.
Manager Erik ten Hag provided no details, instead talking about players who may miss their weekend game against West Ham due to illness.
"We have some doubts, some illnesses during the week," he told reporters at his pre-match press conference.
"We have to see who is available for tomorrow, hopefully they are recovered, we have to see."