Phil Neville has been told he faces a lengthy lay-off after damaging knee ligaments against Fulham.
The Everton skipper was stretchered from the field after a rough challenge from Dickson Etuhu at Craven Cottage.
'An MRI scan on Monday morning has confirmed our fears and it has revealed that Phil has damaged ligaments at the back of his knee,' said Toffees physio Mick Rathbone.
'He will now rest it for 48 hours to allow the swelling to go down and he will then see a specialist in London before a decision is made on how best to manage the injury.
'It's too early to estimate length of absence but I fear he is certainly facing a lengthy lay-off.'
Everton manager David Moyes was unhappy with with Etuhu's tackle in Sunday's 2-1 to Fulham.
Neville's absence means the Toffees have problems at right-back for the visit of AEK Athens on Thursday, with new signing John Heitinga ineligible and Tony Hibbert suspended after being sent off in the second leg against Sigma Olomouc.