West Ham manager Manuel Pellegrini accepts winger Andriy Yarmolenko could struggle to play again this season following Achilles surgery.
The 28-year-old, signed from Borussia Dortmund in the summer, was forced off during the Premier League defeat to Tottenham.
Following an operation, Ukraine international Yarmolenko is now facing a lengthy spell of rehabilitation, which is expected to be at least five months.
Pellegrini understands that to get Yarmolenko, who had scored two goals for the Irons, back firing on all cylinders and ready to make an impact by the start of May might be a tall order.
"Yarmolenko has had surgery and he will be out for around five months. It's very disappointing. He's an important player for us," the boss said.
"He's one of the players who arrived this season, so we could have more technical players. We also have Manuel Lanzini and Jack Wilshere out, so three players in the same position are out.
"It's a real pity and it's really difficult for the team."