Blackburn manager Sam Allardyce fears Gael Givet could endure a spell on the sidelines with a knee injury.
The French defender was replaced at half-time by Ryan Nelsen in Sunday's defeat 3-0 defeat at Everton.
Allardyce says the club are in the dark over the exact nature of the injury suffered by the former Marseille stopper.
However, he fears it could be ligament related as the knock was not inflicted by an Everton player.
"He fell on his knee, we aren't sure of the extent of the damage yet," he told the club's official website.
"But it is a little worrying that is it isn't a kick so he may have twisted or tweaked a ligament."