Celtic skipper Scott Brown had surgery on an abductor problem during the international break and will be out for four to six weeks, manager Neil Lennon has confirmed.
Ahead of tomorrow's Premier League clash with St Mirren in Paisley, the Hoops boss gave an injury update at the club's Lennoxtown training complex.
He said: "Scott Brown had surgery in the break so he is looking at a month, four to six weeks.
"Thomas Rogne has a hamstring strain and he will out for two to three weeks.
"James Forrest (back) is continuing his rehab at the minute.
"Joe Ledley didn't train today, due to a slight groin strain, but will hopefully train tomorrow and Adam Matthews (hamstring) will train on Monday.
"Charlie Mulgrew is fine, he had a tight hamstring before the Serbia game and Gordon Strachan didn't take any chances with him obviously, but he came through training today okay."
Lennon, meanwhile, believes some Scotland players "need to leave their egos at the door" if the national team is to emerge from its current slump.
The 2-0 World Cup qualifying defeat in Serbia in midweek left the Scots at bottom of Group A with two points from six games and confirmed their absence from the finals in Brazil in 2014.
Lennon said: "In terms of the national team, some of the players need to leave their egos at the door and sacrifice a little bit more for their country," Lennon said.
"I am not just talking about the hunger at young level, I am talking about the hunger at senior level.
"I think players are comfortable at their clubs and it looks to me like it becomes a bit of a chore rather than a privilege to play for their countries.
"You look at countries like Montenegro and Uruguay, who are smaller, but they have a real hunger and love for playing for their countries."
ST MIRREN v CELTIC, LIVE TOMORROW, SKY SPORTS 4 (KO 12.45)