Andy Carroll could be set for yet another spell on the sidelines after the injury-plagued striker limped off after just 12 minutes of West Ham's win over Bournemouth.
Carroll scored back-to-back Premier League goals when he returned from his latest injury lay-off over the Christmas period.
However, the England international suffered what appeared to be a muscular leg injury after less than a quarter-of-an hour of his side's 3-1 win at the Vitality Stadium on Tuesday night.
The former Liverpool and Newcastle striker received treatment on the pitch but then hobbled off down the tunnel holding his left leg and shaking his head with his match over.
"It is a really bad situation for us," said Hammers boss Slaven Bilic. "After the Liverpool win I said that he is back, he looked sharp, he looked strong and he was covering the whole pitch and terrorising the difference.
"So, it is a blow but he has been working really hard. Maybe or hopefully it is not that long. Maybe it is going to be a couple of weeks but we need him.
"He is disappointed because he knows he is back but if we have to choose between a knee and hamstring injury it is better to have a hamstring injury."
Carroll, who underwent major knee ligament surgery last February and only returned for the Hammers in September, was making only his seventh league start of the season.
A series of injuries has restricted the 27-year-old to 41 appearances for the club in the Premier League since his arrival on an initial season-long loan in 2012.