Everton manager Roberto Martinez has confirmed that Antolin Alcaraz has suffered a dislocated shoulder.
The 32-year-old had to be substituted during the first half of Saturday's 0-0 draw with Swansea City following a collision with Wilfried Bony.
A subsequent scan has since shown that the Paraguayan's joint popped out of position, which Martinez told reporters will rule him out of action "for a while".
The Toffees boss then went on to reveal: "There is a decision to be made on whether Antolin needs surgery or not."
It is expected that with John Stones also injured, veteran Sylvain Distin will come into the side for tomorrow's Europa League tie against Lille.