West Brom coach Tony Pulis revealed a knee injury kept Ben Foster out of Monday night's 1-1 draw at Leicester.
Albion have yet to determine the extent of the injury, which the 34-year-old goalkeeper sustained during the international break while playing in the garden with his children.
However, Pulis admitted he is worried about the problem given Foster missed 10 months in the 2015-16 season with anterior cruciate ligament damage.
To compound his goalkeeping problems, stand-in Boaz Myhill, making his first Premier League start since April 2016 in Foster's absence, also finished the match at the King Power Stadium with an injury.
"I don't know what happened with Bo as he was taken straight to the drug testers, so I don't know if it was his hamstring, his back or his groin," said Pulis.
"I sent Gouldy [Jonathan Gould, goalkeeping coach] round to ask him if he wanted to come off and he said he was fine.
"Bo was in because Ben has hurt his knee, which is an enormous worry for us because I think he is one of the best goalkeepers in the Premier League. We'll have to check as it might be minor, so it will be scanned.
"We need to find out exactly what it is before we move on and at the moment we don't know exactly what it is.
"He was playing with his son in the back garden and he's just tweaked his knee and because he's had the cruciate we are a little bit concerned. There was no way in a million years we were going to take the risk with him tonight."
Pulis was frustrated his side could not hold on for a third victory of the season.
"Our quality is better than what we showed at times tonight, but you can't fault their effort, commitment and the way they defend by putting their bodies in the way," said the West Brom boss. "We're disappointed obviously but every game is a tough game in this league."