Everton hope midfielder Gareth Barry will be out for "weeks rather than months" with his ankle problem.
Barry sustained the injury in Sunday's 1-1 draw with Sunderland after a heavy tackle by Jordi Gomez.
The 33-year-old was taken to hospital with fears he had broken his leg.
"His ankle is still very swollen, which complicates assessment, but the Everton medical staff have confirmed that there is ligament damage in the area," the club said on its website.
"Although it is too early to estimate a length of absence, it is hopeful the time out will be weeks rather than months."
Leighton Baines equalised from the penalty spot to earn Everton a point at the Stadium of Light after Sebastian Larsson had put the hosts ahead with a curling free-kick.
However, Everton manager Roberto Martinez felt Sunderland striker Connor Wickham and midfielder Gomez should have been sent off by referee Lee Mason.
Wickham was the last man when he conceded a penalty following a foul on Everton right-back Seamus Coleman but was not shown a card.
Gomez was fortunate to escape a second booking when he made the most of minimal contact from Everton defender Phil Jagielka inside the penalty area, which prompted the visiting players to surround Mason.
"It was a clear penalty and it should be a red card. There's no argument and maybe that would have changed the game," Martinez said.
"I don't want to see players red-carded but Gomez had a yellow card then got caught simulating. These are big moments."