West Ham United have confirmed striker Enner Valencia suffered a "significant" injury to his right knee and ankle in Thursday's Europa League qualifier with Romanian side Astra Giurgiu.
The Ecuador international was starting his first Europa League game for the club since returning from the Copa America but he had to be carried off on a stretcher after falling awkwardly in the 37th minute of the third qualifying round first leg tie.
West Ham will have to wait until Valencia has seen a specialist consultant on Monday before they find out how serious the injury to the 25-year-old is and the timescale of his recovery.
A bad night for West Ham
Valencia had put West Ham in the lead with a close-range header before being forced off the field and the injury added to West Ham's problems. The Hammers' hopes of reaching the group stages were dealt a blow after letting a two goal lead slip.
The Hammers' were leading 2-0 with 20 minutes to go but James Collins' dismissal, West Ham's third red card in five Europa League games this season, changed the match. The Romanian side scored two goals in the final 20 minutes, one courtesy of an own goal from West Ham's summer signing Angelo Ogbonna.
The Premier League club now face a tough test in the second leg in Romania on Thursday to progress in this year's Europa League, a competition they qualified for through the Fair Play League.
West Ham's Attacking Options
The Hammers were always keen to bring in a striker in this summer and, following Valencia's setback and Andy Carroll's continuing injury struggles, this has now become more urgent. With the start of the Premier League next weekend and the trip to Romania on Thursday, West Ham will be hoping to bring in a forward as quickly as possible.
A name that has been linked with the club recently is Fenerbahce's Moussa Sow, who has already been the subject of a failed transfer bid from Premier League rivals Sunderland.
West Ham could also renew their interest in Javier Hernandez from Manchester United. The Mexican spent last season on loan at Real Madrid, where he scored nine goals in 33 appearances.
Another option could be Hernandez's compatriot, Raul Jimenez, who may be available on loan from Atletico Madrid. The 24-year-old started just four La Liga games for the Spanish club last season after becoming the fourth choice striker following the arrival of Fernando Torres in January.