West Ham United winger Andre Ayew faces a "significant rehabilitation period" through injury, the club have announced.
Ayew, 26, limped off in the first half of Monday's 2-1 Premier League defeat to Chelsea at Stamford Bridge.
The club's head of medical and sports science, Stijn Vandenbroucke, confirmed the forward is set for a lengthy period on the sidelines, while Jack Sullivan, son of co-chairman David Sullivan, has said he will be out for for months.
"Andre Ayew injured his right thigh at Chelsea on Monday and underwent a scan on Wednesday afternoon," Vandenbroucke said.
"The medical team will now assess the results with a leading consultant before drawing any conclusions.
"My first thought and priority is with the player and his physical and mental wellbeing. He has suffered a significant injury and it is imperative that we do not rush to conclusions and we receive the correct diagnosis by consulting top specialists.
"At this time, it is too early to put a timeframe on his potential return date but Andre is facing a significant rehabilitation period.
"The best thing we can do as a Club is to support Andre through this difficult period. We will keep you updated throughout this process and I am sure he will be come back stronger than ever."
Ghana international Ayew signed for the Hammers from Swansea in the summer, having scored 12 Premier League for the Welsh club last season.