Manager Ange Postecoglou confirmed Leigh Griffiths had missed Celtic's crucial trip to Denmark with a "slight injury".
Striker Griffiths is out of Wednesday's Champions League qualifier against Midtjylland, who drew 1-1 at Parkhead last week, but Albian Ajeti has recovered from the issue which forced him to miss Saturday's 6-2 friendly defeat by West Ham.
On Griffiths, Postecoglou said: "He picked up a slight injury yesterday (Monday) in training, which was disappointing for him because he was obviously going to be part of the travelling party.
"Albie trained yesterday and he is fine, so he will be involved. Everyone else from the weekend, apart from Leigh, pulled up fine."
Griffiths was booed by a section of fans during the Hammers loss following recent police and club investigations into his social media activity.
Police Scotland said it had established "no criminality" after carrying out a "full assessment" of claims that the 30-year-old had exchanged improper messages with a 15-year-old girl as well as another teen girl, and he returned to the fold for Celtic last week.
Postecoglou said: "In terms of the crowd response, Leigh is in the same position as all of us. We represent the football club and the supporters are there to judge us on how we perform and what we do. We have to accept any response we get from them.
"For the most part Leigh still got a positive response from the crowd because they acknowledge the fact that he has had a very good career at Celtic and has contributed.
"If there are people who express dissatisfaction, it's up to him to show with his performances and the way he goes about things, I am sure he can win them back very quickly."
Celtic travelled to Denmark with an inexperienced back-line following Nir Bitton's first-leg red card.
But new signing Carl Starfelt is set to be available for Saturday's cinch Premiership opener against Hearts, with the Sweden centre-back in quarantine in London following his move from Rubin Kazan.
Postecoglou, who added that Christopher Jullien faced another "couple of months" out as he battles back from a knee injury, said: "Carl has started some individual training and we are hoping he joins us at Lennoxtown by the time we get back to Scotland.
"We will see what his condition is like then but he should be available by the weekend."