West Ham forward Marko Arnautovic has vowed to "come back strong and quick" as he prepares for a number of weeks on the sidelines.
The Austrian was forced off after just 40 minutes on Tuesday night, though his replacement, Lucas Perez, went on to score twice as West Ham beat Cardiff 3-1 at the London Stadium.
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 (sic).
"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".
Standard Sport understands the forward will miss the entire festive schedule and Manuel Pellegrini is expected to confirm the layout at his pre-match press conference on Thursday ahead of the weekend fixture against Crystal Palace.
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.
