Everton fear midfielder Ross Barkley could face an extended lay-off after injuring his hamstring in training on Monday.
The 23-year-old, who is the subject of transfer interest from Tottenham, Chelsea and Arsenal, had only just returned to training last week following a hernia operation.
Teammates saw him go down in pain clutching his leg during the session at Finch Farm and the England international had to be helped from the field.
He is due to undergo a scan to determine the full extent of his injury.