Everton midfielder Darron Gibson is to undergo surgery after suffering anterior cruciate ligament damage, the club have announced.
Gibson was carried off on a stretcher after injuring his knee in a first-half challenge during the Republic of Ireland's World Cup qualifier against Kazakhstan in Dublin on Tuesday.
The 25-year-old was assessed by club medical staff on his return to Everton and, following confirmation an operation will be required, a lengthy lay-off is likely.
A statement on the club's website, evertonfc.com, read: "The length of time the 25-year-old will be best determined once the surgery is completed.
"However, the scans did confirm to Everton's medical team that no additional damage was sustained to the structure of the right knee, ensuring all treatment and rehabilitation will be focused on repairing the damaged ACL."
The injury is fresh blow for the player after missing the start of the season with a different knee problem.
His return to fitness, to feature in his first Barclays Premier League game of the season against Manchester City on October 5, preceded his recall to the international scene last week.
Gibson made himself unavailable after Euro 2012 but the recent departure of manager Giovanni Trapattoni led to a recall for Ireland's final two World Cup qualifiers by interim boss Noel King.
He played 90 minutes against Germany last Friday but lasted just 37 against Kazakhstan, a match which was watched by his club manager Roberto Martinez.
After the game King said the injury "wasn't nice" and now Everton, who have made a positive start to the season mostly in his absence, will have to continue without him.
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