West Ham face losing Kurt Zouma for the remainder of the season.
West Ham are fearing the worst over his ankle injury, with reported concerns that he could be out for the rest of the season.
Zouma suffered the issue during the first half of the Hammers' 2-0 Premier League defeat at Brentford on Sunday.
On Tuesday, West Ham confirmed that Zouma wouldn't play in Thursday's Europa League quarter-final second leg at Lyon as a result. The scoreline is evenly-poised at 1-1.
"The France international defender is to remain in London for further tests and examination on the ankle injury," they said in a statement.