West Ham manager Slaven Bilic was left fretting over Diafra Sakho's fitness after he was forced off injured in Sunday's 1-1 Premier League draw with West Brom at Upton Park.
Sakho was hurt late in the second half as Jonas Olsson deflected his goal-bound shot into the side netting, with Bilic more worried about that than the two points dropped, his side having gone ahead through Mauro Zarate's superb free-kick before Winston Reid's own goal ensured the spoils were shared.
"Losing Diafra Sakho worries me more than the result," Bilic said.
"Before the scan it is difficult to diagnose, but it looks a muscle injury."
Sakho has hit five goals this season, but has not found the net since late September, although he missed a month of action after rupturing his thigh.
West Ham's attacking options are already limited as Enner Valencia is out for a month with an ankle injury and Dimitri Payet is not expected to return until next year.
"It's a big blow for us, he's a key player," added Bilic.
Nikica Jelavic replaced the Senegal international striker, who limped straight down the tunnel, but West Ham could not find a winning goal as their patchy home form continued.
