Celtic manager Brendan Rodgers has confirmed that Australia international Tom Rogic needs knee surgery and will be sidelined until mid-March.
The 26-year-old former Central Coast Mariners midfielder will be out of action for up to six weeks.
Rogic has been representing the Socceroos at the Asian Cup, which was surprisingly won by Qatar, with Graham Arnold's side being knocked out in the quarter-finals by United Arab Emirates.
"Tom is actually going to be out for six weeks which is a real blow for us," Rodgers said ahead of Sunday's trip to St Johnstone.
"He came back from the Asian Cup and had an issue with his hand out there and injured his knee when he landed awkwardly.
"He went down to London with a member of our medical team to check that his hand didn't need an operation and, while he was there, we thought we would have his knee looked at and it showed up a lateral meniscus problem, which is going to put him out for up to six weeks.
"It is not what we expected but that's the way football works. It is unfortunate. He won't need the operation on his hand but needs it on his knee."
Celtic are 1/8 to win the Scottish Premiership again this season and 3/10 to beat St Johnstone in Perth on Sunday.