Leigh Griffiths will remain at Celtic’s training base in Lennoxtown to improve his fitness rather than join the squad for pre-season friendlies in France.
He will miss the matches against Nice on Thursday, host club Lyon on Saturday and the final game against Paris St-Germain in Paris on 21 July.
The 29-year-old striker scored 11 times in 31 matches for Celtic last season.
“Leigh is undertaking his own fitness programme along with some other players at Lennoxtown,” said Celtic.
“He will team up with the squad when they return from France.”
It had been reported in the Daily Record that Griffiths had returned to training last month “out of condition” and was not part of the squad’s pre-season camp at Loughborough.
The Scotland international missed part of last season through injury and personal problems.
His goal in Celtic’s 2-1 win over Partick Thistle in the Scottish Cup in January was his first in five months.
Manager Neil Lennon has Odsonne Edouard, Patryk Klimala and Vakoun Bayo as his main striking options, while Ryan Christie and Michael Johnston also offer an attacking threat.