Burnley captain Josh Cullen is set for a “prolonged period on the sidelines” after sustaining an anterior cruciate ligament in his right knee.
The Republic of Ireland midfielder suffered the injury early in the second half of Saturday’s 0-0 draw with Everton before being replaced by Florentino Luis.
Cullen had scans on Monday which confirmed the injury and the 29-year-old is set to undergo surgery.
“Everyone at Burnley Football Club wishes Josh all the best for a successful and speedy recovery,” the Clarets said in statement.
Cullen started all 18 games of the season before missing Burnley’s 3-1 defeat at Newcastle on Tuesday.
Scott Parker’s side are 19th in the Premier League and six points from safety after suffering eight defeats in their past 10 games.
They have not won since a 3-2 victory at bottom side Wolves on 26 October.