West Ham defender Winston Reid has been ruled out for more than a month after dislocating his shoulder during Tuesday's 0-0 draw with Bristol City.
The New Zealand international, 23, went to hospital for a scan after lasting just seven minutes of the clash.
Boss Sam Allardyce told the club website: "If we are lucky he will be out for four to five weeks, if it doesn't need an operation or pinning."
Allardyce is also waiting to learn the extent of John Carew's knee injury.
The Norway international striker missed the clash with the Robins at Upton Park and is doubtful for Saturday's trip to Hull.