Everton midfielder Darron Gibson will have surgery after suffering cruciate knee ligament damage and could miss the rest of the season.
Gibson was carried off on a stretcher after landing awkwardly during the first half of his country’s 3-1 victory over Kazakhstan in a World Cup qualifier in Dublin on Tuesday.
Having returned to Merseyside to be assessed on Wednesday, Gibson will need an operation, Everton have confirmed - although they did not say how long he would be out for.
The club said in a statement on their website: "A subsequent scan showed he has damaged his anterior cruciate ligament (ACL) and the midfielder will require an operation.
"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 focussed on repairing the damaged ACL."
Republic of Ireland interim manager had told reporters earlier on Wednesday that he feared a lengthy absence for Gibson.
"I feel very bad for Darron Gibson; he’s not good," King said. "It’s awful. It might be a few months. It won’t be easy for him to get back this season."
Gibson, who was being watched at the Aviva Stadium by his club manager Roberto Martinez, has only recently returned to Everton’s starting line-up after missing the opening weeks of the season with a knee injury.
The midfielder was making only his second appearance for his country since ending a 16-month self-imposed exile.
He quit the Republic set-up after a fall-out with coach Giovanni Trapattoni, who left him on the bench for all three matches at Euro 2012.
But the former Manchester United midfielder made himself available again after Trapattoni left his post in September, and played in Friday’s 3-0 defeat against Germany in Cologne.
Gibson has played only twice for Everton this season.
Martinez said only last week that he felt Gibson’s return to international duty would help Everton.