Gylfi Sigurdsson could be ruled out for the rest of the season after it emerged the Icelandic midfielder has "very damaged" ligaments in his right knee that were sustained during Everton's 2-0 win over Brighton, according to Scandinavian outlet Fotbolti.
The 28-year-old played the full 90 minutes against the Seagulls on Saturday as Gaëtan Bong's own goal and a thunderous strike from Cenk Tosun gifted Sam Allardyce's side all three points.
However, it is claimed Sigurdsson played through the pain to see the game out as opposed to seeking a substitution - a decision that could rule the Iceland international out until 2019 if he has to undergo surgery.
The Toffees have confirmed that Sigurdsson will see a specialist to determine the extent of his injury on Monday.
Sigurdsson moved to Everton in the summer and has been unable to replicate the same form he showed during his time with Swansea, scoring just four goals and claiming three assists following his £45m transfer.
The midfielder's arrival was initially questioned as a result of Everton's other transfer dealings last summer, with the club also siging fellow playmakers Wayne Rooney and Davy Klaassen.
However, Sigurdsson has proved to be one of Everton's most important players this season, missing just two Premier League games.