Everton boss Roberto Martinez has admitted they fear Romelu Lukaku suffered an ankle ligament injury in Tuesday's 4-0 defeat to Liverpool.
On-loan striker Lukaku was stretchered off just after Liverpool's opening goal at Anfield after colliding with Everton team-mate Gareth Barry while defending a Liverpool corner.
Martinez admitted the injury is causing them concern and is waiting to find out the full extent of the problem.
"We're going to assess it," he said. "At the moment he's got his ankle in a cast and it doesn't look too good.
"He just collided with Gareth Barry at the corner as the ball was delivered into the box. It's there where he twisted his ankle."