West Ham have suffered a double injury blow, with defenders Winston Reid and Sam Byram likely to miss the rest of the season.
Reid was taken to hospital after twisting his knee during the Hammers' 4-1 defeat to Swansea on Saturday.
The 29-year-old played for the first time in almost two months at the Liberty Stadium but, after also being knocked unconscious and receiving oxygen on the pitch, he was replaced by Byram after just 27 minutes.
The absence of the New Zealand centre-back is a major blow to the Hammers' bid to stay in the Premier League.