West Ham defender Angelo Ogbonna has been ruled out for the rest of the season with a knee injury.
The Italian played all 90 minutes in Saturday's 3-1 win at Middlesbrough but has been carrying the injury throughout the campaign.
West Ham boss Slaven Bilic asked him to delay surgery earlier in the season while his squad was stretched but the arrival of Jose Fonte from Southampton will offset Ogbonna's absence.
Bilic said: "I have to praise Angelo Ogbonna, because he has played the whole season with an injury.
"He needs an operation on his knee to be fit long-term, and it was supposed to be a couple of weeks but we asked him to play.
"Ogbonna will now have surgery which will rule him out until the end of the season."
Co-owner David Sullivan told the club's website: "We of course wish Angelo all the best with his knee surgery and for a successful rehabilitation.
"Angelo has showed his commitment to the club by playing with the injury for a while now, and we thank him for that.
"We have signed Jose Fonte and he is a top-class defender who will add strength, depth and leadership to our squad.
"When we knew Jose was available, we made him a top target and were delighted to beat off some big clubs for his signature. It is a big statement of intent."