West Ham winger Michail Antonio will miss the rest of the season through injury.
The 28-year-old limped out of last weekend's 3-0 win over Southampton with a hamstring problem and will have an operation in the coming days.
Antonio's latest setback in a season beset by injuries has also ended any slim chance he had of making England's World Cup squad.
Hammers manager David Moyes said: "He is out for the season. He is going to have an operation on his hamstring and the biggest thing now is to get him ready for the start of next season.
"He's a big miss, someone we need. He has great pace, great strength and we will miss him until the end of the season.
"They tell me last season he had very few injuries, but he picked up one at the end of the season with his hamstring and he's never really recovered from that.
"In the time I've been here he's had a few pretty bad injuries. It is what it is, we have to get on with it. He's a miss to us and we hope we can get him back quickly for the start of next year.''
Midfielder Manuel Lanzini also looks set to miss Sunday's trip to Chelsea with the knee injury he suffered on international duty with Argentina.
"He's back running, but he was running last week,'' added Moyes.
"He's got a medial ligament injury which is affecting his turning and twisting. I wouldn't completely rule him out but at the moment he's a doubt.''
The win over Saints not only lifted West Ham clear of the drop zone, it also lifted the mood around the whole club following the protests and pitch invasions which marred their previous match against Burnley.
Victory at Stamford Bridge would ease their relegation fears further, and see the Hammers do the double over their London rivals following a 1-0 home win in December.
"What it got us was three really important points but we are keeping our focus, we haven't got enough points to be safe yet,'' said Moyes.
"We have to pick up more. The next game is Chelsea and we have to try and pick up points in that. It was a really big win for us, for the team, for the club, it gave us all a boost.
"Now I hope lightning can strike twice and we can do it again against Chelsea.''