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 .
But they have suffered a further setback as right-back Byram could also miss the rest of the campaign with an ankle problem he picked up in the same game.
David Moyes' side are 14th, three points above the relegation zone, with nine games remaining.
The Hammers have lost successive games 4-1, to Liverpool and Swansea, and play at home to Burnley on Saturday.
There is some better news for the Hammers, with Angelo Ogbonna is set to return following illness. James Collins could be also back from a hamstring strain.
Arthur Masuaku's six-game ban for spitting will end after the Burnley clash.