Ireland defender Joey O'Brien faces an absence of around three months after dislocating his shoulder in West Ham's Barclays Premier League draw at Chelsea.
Manager Sam Allardyce confirmed the defender will miss a significant chunk of the Hammers' fight to avoid relegation.
O'Brien landed awkwardly following an off-the-ball push from Chelsea defender Gary Cahill as the players positioned themselves at a corner, leaving the Hammers to defend stoppage time with 10 men.
"The only disappointment for us today was the two injuries," said Allardyce, following the 0-0 draw at Stamford Bridge.
"Joey, unfortunately, has dislocated a shoulder, which is bad news for us.
"That's our third dislocated shoulder this season. I don't think I've had three dislocated shoulders in my entire career, let alone three in one season."
Asked the likely length of absence, Allardyce said: "Ten to 12 weeks."
Mohamed Diame will be assessed ahead of Saturday's home match with Newcastle after suffering a bang on the knee when he fell over the advertising hoardings and had to be replaced in the first half.