West Ham striker Andy Carroll is facing up to six weeks out of action with a hamstring injury.
The 27-year-old was substituted after just 15 minutes in the Hammers' 3-1 win at Bournemouth.
Carroll had scored two goals in West Ham's past four games after returning to action in September 2015, following seven months out for knee surgery.
"He's a positive lad, but of course he is gutted for several reasons," said Hammers boss Slaven Bilic.
"He felt he was back and enjoying his football.
"It's not the end of the world, though. If everything goes well he will be back very soon so there is no reason to be negative.
"If it goes as we expect, then he will be back for a significant part of the season, the last 10-15 games, with enough time to make a huge impact on our season."
Carroll has won nine England caps and scored twice but has not played for the national team since a World Cup qualifier against San Marino in October 2012.
West Ham are fifth in the Premier League, just a point behind fourth-placed Tottenham with 17 games remaining.