Marko Arnautovic has vowed to "come back strong and quick" for West Ham as he looks set to be "out for a while" with a suspected hamstring problem.
The Austria striker, who has scored five goals this season, was forced off during the first half of Tuesday night's 3-1 Premier League win over Cardiff.
Arnautovic posted pictures of his leg in a straight knee sleeve and said on his Instagram story: "Lets Go I will do everything to be back for my team @westham.
"Thank you so much for all your messages. I will be out for a while but will do everything to come back strong and quick."
West Ham have yet to confirm the full extent of Arnautovic's injury, but wished the forward a speedy recovery in a post on the club Twitter account, which said: "Get well soon, Arnie".
Hammers boss Manuel Pellegrini is set to hold a pre-match press conference on Thursday ahead of the weekend fixture against Crystal Palace, when more is expected to be revealed on Arnautovic's expected lay-off.
Depending on the extent of the problem, Arnautovic could struggle to feature over the festive schedule.
West Ham have a home match against Watford on December 22, then are away at Southampton on December 27 before a trip to Burnley and hosting Brighton on January 2 with an FA Cup third-round date versus Birmingham set for three days later.
The Hammers recovered from the loss of Arnautovic to make it back-to-back Premier League wins for the first time in almost two years by beating Cardiff.