London - West Ham United's Ecuador forward Enner Valencia suffered a "significant injury" in Thursday's 2-2 draw with Astra Giurgiu in a Europa League third qualifying round first-leg tie, the club said in a statement.
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"Enner Valencia sustained what initially appears to be a significant injury to his right knee and right ankle..." the Premier league club said on their website (www.whufc.com).
The 25-year-old opened the scoring at Upton Park with a close-range header but fell awkwardly and was forced to leave the field on a stretcher after 35 minutes. He was taken straight down the tunnel for further treatment.
Valencia will see a specialist on Monday but the east London club said it was too early to put a timescale on how long his recovery and rehabilitation would be.
Valencia, who scored three goals during an impressive World Cup campaign in Brazil last year, joined West Ham after the finals on a five-year contract from Mexican side Pachuca.