Celtic defender Daniel Majstorovic is set to miss the next six weeks of the season, the Glasgow giants said on Tuesday.
The Sweden centre-back fractured his cheekbone during the first half of the 2-0 victory away to St Johnstone in the Scottish Premier League on Sunday.
Although an operation on Monday was deemed to be successful, he is unlikely to be back in training with the Hoops until February at the earliest.
"Daniel Majstorovic underwent surgery yesterday (Monday), on the fractured cheekbone he suffered in the 2-0 win against St Johnstone on Sunday," a Celtic statement said.
"The operation went well, but he now faces six weeks on the sidelines before he can return to training."
There was better news for Celtic with the return to training of midfielder Joe Ledley following an ankle injury, and he is expected to be available for this weekend's match at home to Kilmarnock.
Celtic are currently four points behind SPL leaders and arch rivals Rangers, the reigning Scottish champions.