West Ham United defender James Tomkins has undergone surgery on his dislocated shoulder.
The 25-year-old picked up the injury during a training session last week and is expected to miss the majority of the Premier League run-in as a result.
The club's head of medical and sports science Stijn Vandenbroucke also confirmed that Doneil Henry will have an operation on the hamstring injury he sustained while on loan at Blackburn Rovers and that Winston Reid is nearing a return to fitness.
"Unfortunately, we have had two setbacks in the defence. James Tomkins underwent successful surgery on his dislocated shoulder on Wednesday and will now commence his rehabilitation, with a view to him returning to fitness before the end of the season," Vandenbroucke told the club's official website.
"Doneil Henry injured his hamstring during his loan spell with Blackburn Rovers and, after consulting with a specialist, he will have an operation at the end of the week.
"Winston Reid is recovering and rehabbing well from the hamstring injury he suffered against Chelsea on 4 March. He is working hard on his fitness and is getting closer to a return."
The Hammers, who were forced to utilise Cheikhou Kouyate as a makeshift centre-back during the 3-0 defeat to Arsenal last weekend, face Sunderland at Upton Park on Saturday as they go in search of a first win in nine.