Everton will find out the extent of Leighton Baines' ankle injury this week after Roberto Martinez confirmed the defender had been sent to see a specialist.
Baines was substituted after 74 minutes of Everton's 2-0 defeat to Sunderland at Goodison Park on Saturday having picked up the injury.
It is the latest frustration for the England international, who has already missed parts of the season with hamstring, thigh and knee problems.
"We're going to find out a bit more in the next two days," Martinez told the club's official website.
"It was really, really painful in an area that has been a bit of a problem for Leighton.
"We'll get more clarity over the next 48 hours and clearly we'll address it once we get that information from the specialist."
Everton travel to Upton Park to face West Ham this weekend, before finishing the Premier League campaign at home to Tottenham.
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