West Ham star Andriy Yarmolenko is set for six months on the sidelines after undergoing surgery on a damaged Achilles tendon.
Yarmolenko has scored two goals in nine league appearances for West Ham this season, having also sustained an Achilles injury last term with Dortmund.
Both goals came in a 3-1 win over Everton at Goodison Park, which was West Ham's first victory of the season.
With the Hammers confirming an expected six-month lay-off, head of medical services Richard Collinge said: "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."
The injuries come at a bad time for the club as Manuel Pellegrini's side have hit their second rough patch of the campaign.
West Ham started the season slowly, losing their opening four Premier League contests, but had seen an improvement, picking up 10 points from a possible 12 in their next four fixtures.
However, the Hammers have not dropped two straight games with the loss to Spurs coming on the heels of a 1-0 defeat to Brighton prior to the international break.