Roy Hodgson has warned that Crystal Palace expect to lose Mamadou Sakho for an extended spell on the sidelines.
The summer signing was forced off with a calf injury against Bournemouth at the weekend, and doctors are reluctant to put a date on a return to training.
"It's far too early [to tell]," Hodgson told reporters.
"It's a serious muscle strain or tear and the doctors won't put a timescale on that. It's going to be a while that's for sure."
Palace are also sweating over the fitness of loanee Timothy Fosu-Mensah, who on Thursday will undergo a scan on a hamstring injury picked up during Tuesday's dramatic win over Watford.
The three points over Marco Silva's side temporarily moved Palace out of the relegation zone for the first time this season, until West Brom earned a point at Anfield the following night.
Hodgson is keen to temper expectations in light of a six-game unbeaten streak but underlined his happiness at the progress made since his appointment.
He added: "Nothing has changed for me or my staff. We have worked exactly the same way since we came in.
"We can only hope to continue with what we've achieved so far. We aren't the finished article.
"We are closer to the pack and thats the important thing. There is going to be a pack of teams for a period of time going forward in and around that third spot.
"Now we have ourselves within three or four points of that pack, it's important we stay with them."
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