Valencia hammer-blow for West Ham
West Ham striker Enner Valencia suffered an apparently "significant" injury to his right knee and right ankle in the Europa League clash with Astra Giurgiu on Thursday night.
The Ecuador forward, who was starting his first game since returning from the Copa America, was taken off on a stretcher before half-time.
Manager Slaven Bilic said after the game he feared the injury was serious, and an update from West Ham on Valencia's health indicated he was right to be worried.
Valencia could face a long absence from first-team availability, but West Ham will wait for him to visit a specialist at the start of next week before forecasting how much of the season he stands to miss.
The news will come as a blow to the Hammers, who are already without club-record signing Andy Carroll for the start of the new season.
Valencia enjoyed an impressive start to his career at Upton Park after joining last summer but his goal in Thursday night's 2-2 draw was only his third in front of West Ham's home support.
Diafra Sakho was suspended for the meeting with Astra, but the the Senegal international can play the return leg in Romania next week, with the Hammers needing to to win if they are to advance.