Celtic manager Ange Postecoglou does not have a timescale for Kyogo Furuhashi's return to action but expects to be without the striker for "a number of weeks".
The Japan international missed three games in December with a hamstring injury then only played 15 minutes against St Johnstone on Boxing Day before being substituted.
He did not feature when Celtic returned from the winter break with a win at home to Hibs and Postecoglou does not expect him to play any part over the next few weeks, including in the Old Firm clash against Rangers on February 2, live on Sky Sports.
"We are still sort of working through that but suffice to say it's not going to be a quick return," the Celtic boss said.
"I'm reluctant to put any timeframe on it, just for the player himself. I think it's unfair that I do that, but we are still looking at a number of weeks at the moment.
"Hopefully we will get some clarity, there are still some things they want to see if it settles down, but we are looking at a number of weeks at this point."
Rogic on international duty
Celtic midfielder Tom Rogic has been ruled out of next month's Old Firm fixture against Rangers after Australia named him in their squad for their upcoming World Cup qualifiers.
The 29-year-old will also miss games against Hearts and Dundee United after Socceroos head coach Graham Arnold rewarded him for his impressive form by calling him up for the matches against Vietnam and Oman.
Postecoglou is happy to do without the in-form player for those matches.
"I'm not disappointed, he's seen selected for his national team because he's a hell of a player and I'd be disappointed if he wasn't selected for his national team," said the former Australia boss.
"Tom's been an outstanding servant for this football club and he's been an outstanding servant for his national team and he wants them to go to their fourth consecutive World Cup.
"On form he's arguably been the best player in the competition here and I want to see him do well for the national team, not just because it's Australia."
Celtic will learn on Saturday if any other players have been called up for international duty, with new signings Daizen Maeda, Yosuke Ideguchi and Reo Hatate all available for Japan selection.
O'Riley is a good fit for Celtic
The manager is delighted to have a new signing to call upon after Matt O'Riley joined from MK Dons on a four-and-a-half-year deal.
"I'm very pleased to get him in," Postecoglou said. "He's a player that we've scouted for quite a while.
"I became aware of him when I joined the club in the summer and he was one of the ones we were looking at and it didn't quite work out then.
- Celtic sign midfielder O'Riley from MK Dons
- Postecoglou: Griffiths' Celtic career is over
- Scottish Premiership returns: What is at stake?
"We followed his progress through the first half of this season with MK Dons and he's had a really strong season.
"I just see some really good football attributes in him that'll fit in well with what we're doing here.
"He's also an outstanding young man who really wants to get the most out of his career and that'll fit really well culturally here.
"It was one we could do quickly, which was also really important to me, because it means he can come in and slot in straight away. I'm pleased to get him in."