The Poland international suffered the injury during the first half of the Hammers’ 2-2 draw at Bournemouth on Saturday and there is no specific time frame on a first-team return for the 34-year-old. He was replaced by second-choice goalkeeper Roberto, who is now expected to have an extended run in the team, with third-choice David Martin set to step up as his understudy. Fabianski has established himself as the No 1 goalkeeper at West Ham since joining from Swansea last summer for £7m and has kept three clean sheets this season.
Hammers boss Manuel Pellegrini described Fabianski as one of the best goalkeepers in the Premier League on Friday, so his absence will be keenly felt as West Ham attempt to stay in and around the top four. West Ham next host Crystal Palace at the London Stadium on Saturday evening, live on Sky Sports Premier League.