Tom Rogic faces a lengthy spell on the sidelines after undergoing surgery on an ankle injury.

The Celtic midfielder has been ruled out for "a few months" after suffering the knock during a training session in December.

Rogic was spotted in London earlier this week on crutches and his manager, Brendan Rodgers, confirmed at the club's media conference on Thursday he would be out of action for longer than first anticipated.

Rogic, who hasn't played since his side's 2-1 win over Dundee the week before Christmas, was originally expected to be fit in time for the Old Firm fixture on Hogmanay.

"It was unfortunate, it was right at the end of training and the same spot where he had it before," Rodgers explained.

"It was a big disappointment because he was a player I was really looking forward to seeing back playing in this team but he'll be back before the end of the season.

"It's a disappointment he'll miss maybe up to eight weeks.

"He got his foot stuck in the ground and did a full twist on it so it was either go through the same procedure as before or have an operation. He went to London, had an operation and it's all done. He's on his way to recovery now."

The Australian has featured 27 times so far this season and scored 10 goals.