West Ham United concede Enner Valencia's injury is serious.

Valencia broke down in the Europa League clash with Astra Giurgiu.

The club said in a statement on their website: "Enner Valencia sustained what initially appears to be a significant injury to his right knee and right ankle during Thursday's UEFA Europa League third qualifying round first leg tie with Astra Giurgiu.

"The Ecuador forward will see a specialist consultant at a clinic in central London on Monday morning and an update will be provided following that meeting.

"It is too early to put a timescale on how long Enner's recovery and rehabilitation period may be."