Slaven Bilic hopes signing Andre Ayew can make a quick return to action for West Ham after suffering a thigh problem against Chelsea on his debut.
Ayew, 26, joined West Ham in a club-record £20.5 million deal from Swansea but is now a doubt for Thursday's Europa League playoff against Astra Giurgiu.
"Ayew has a thigh injury, he told me it's not a big one but you never know," Bilic said. "He will have a scan and we have to wait for the result of the scan to know how long he will be out."
Sofiane Feghouli is also struggling with a hamstring injury, while Dimitri Payet will continue to be eased back into action after starting on the bench at Stamford Bridge.
Bilic believes the France international still needs time to hit top speed after his exploits at Euro 2016.
"Feghouli picked up something against Juventus which we didn't think was an injury and he trained for a week but he is injured," Bilic said. "It was a plan for Dimitri to come on for not more than half an hour.
"I spoke to him yesterday, he felt good and he looks good in training, but he's not ready yet for 90 minutes. It was the plan to bring him on. He gives you composure, he creates opportunities and space for other players."