West Ham's Victor Moses will undergo a scan after he suffered an injury in the 0-0 Premier League draw at Manchester United on Saturday.
Moses came off holding the back of his leg in the 37th minute during the stalemate at Old Trafford.
The East London club are already without Dimitri Payet, Enner Valencia and Diafra Sakho due to injury.
And manager Slaven Bilic said: "We have to wait for a scan on Victor. It is painful to be without so many key players. But we replaced them today and deserved a point."
United were held to just one shot on target by West Ham, who twice hit the post, with a Chris Smalling clearance that deflected off Mauro Zarate striking the woodwork before Winston Reid did the same with a header.
Zarate also wasted a golden chance, lashing wide from inside the six-yard box.
Of his side's performance, Bilic said: "United had their chances but we defended great as a team. We had the best chances of the first half and should have been in front.
"They put us under pressure in the second half but not many times we come here and get a result especially with the players missing."
