West Ham defender Winston Reid is expected to miss the rest of the season with a knee injury.
The absence of the 29-year-old New Zealander would be a major blow to the Hammers' bid to stay in the Premier League.
Right back Sam Byram, 24, could also miss the rest of the campaign with an ankle problem.
Reid played for the first time in almost two months at Swansea last Saturday, but was replaced by Byram after 27 minutes having been knocked unconscious.