Phil Jagielka could miss Everton’s FA Cup semi-final against either West Ham or Manchester United.
Jagielka was substituted during the latter stages of last weekend’s 1-1 draw at Watford as the Blues captain left the field clutching his hamstring.
The 33-year-old is almost certain to miss Wednesday’s trip to Crystal Palace as Everton’s medical staff attempt to diagnose the full extent the problem.
But Jagielka also faces a battle to be available in time for the Wembley showdown in a fortnight’s time, on April 23.
Roberto Martinez is already braced for life without the defender in the forthcoming games, which includes a Merseyside derby with Liverpool, and believes Ramiro Funes Mori is a more than capable stand-in.
He said: “The injury is a concern, especially with Jags enjoying his football.
“He’s our leader and you know how significant that is. We hope that he’s going to recover quickly and see how he is.
“We’ll address it but at the same time it shows you that we’ve got a very good replacement when Ramiro Funes Mori, a full Argentina international, comes on the pitch to replace him.
“It shows you this squad is built to be competitive and it can cope with suspensions and injuries.
“So we will hope Jags is back for the next game but if that’s not the case we’ll make sure the team is ready without him.”