Gylfi Sigurdsson: Everton midfielder out for "six to eight" weeks
Everton midfielder Gylfi Sigurdsson will be out for "six to eight weeks" with a knee injury.
The Iceland international, the Toffees' record signing, completed Saturday's 2-0 win over Brighton but could now miss the rest of the club's season.
Sigurdsson, 28, who joined the Blues from Swansea for £45m in August, saw a specialist on Monday.
"We'll continue to assess Gylfi's progress on a week-to-week basis," said manager Sam Allardyce.
If he does not recover before the end of Everton's campaign, in a little over eight weeks, it would throw into doubt his chances of featuring in Iceland's first World Cup in Russia this summer.
His brother, Olafur Mar Sigurdsson, told Icelandic media the player had damaged the joint of his right knee.
Sigurdsson's injury represents a significant blow to Everton, who are hoping to finish the season on a positive note after a disappointing start.
He endured a difficult opening to his Toffees career but his fortunes have improved since Allardyce replaced Ronald Koeman in late November.
He has scored five of his seven goals in his 17 matches since then and no Everton player has created more goalscoring opportunities than Sigurdsson.