Everton striker Romelu Lukaku has reportedly suffered ankle ligament damage.
The Belgian forward was brought off for Steven Naismith after pulling up midway through the first half of the Merseyside derby against Liverpool.
According to BT Sport, Lukaku is feared to have suffered a serious injury, although it is not yet clear how long the problem is likely to keep him on the sidelines.
Liverpool lead 3-0 at half time thanks to a Steven Gerrard header and two goals from Daniel Sturridge.