West Ham winger Andriy Yarmolenko will be sidelined for around six months after undergoing Achilles surgery, the Premier League club have announced.
The 28-year-old was forced off during the defeat to Tottenham at the weekend and the Hammers on Monday confirmed the Ukraine international "has undergone successful surgery to repair a damaged Achilles tendon".
Yarmolenko, who has scored two goals in 10 games for West Ham after joining from Borussia Dortmund in the summer, faces a long spell on the sidelines.
West Ham's head of medical services Richard Collinge told the club's website: "Andriy's operation went well and we will now work hard to support him throughout the rehabilitation process.
"His recovery will be planned very carefully and we have every confidence that he will return to full fitness within the scheduled timeframe."
West Ham have completed the signing of Ukraine international Andriy Yarmolenko from Borussia Dortmund for an undisclosed fee.
The 28-year-old forward has agreed a four-year contract with the Premier League club.
Yarmolenko's transfer to the London Stadium continues the recruitment drive of new Hammers manager Manuel Pellegrini, which includes the arrival of Jack Wilshere.
"Of course, I am very happy to sign for West Ham United. West Ham is a big club with good fans and I am happy to come to play in the Premier League," Yarmolenko told the club website.
"The Premier League is the best league in the world and I know that an interesting project is being built here at West Ham.
"The team wants to achieve high things and I am excited for this challenge."