CELTIC boss Neil Lennon fears midfielder Nir Biton and winger James Forrest could both be facing extended periods on the sidelines.
Israel international Biton picked up a suspected thigh tear during his nation's 2-1 friendly loss to Slovakia.
Scotland winger Forrest, meanwhile, was forced to pull out of Gordon Strachan's squad ahead of last week's friendly win in Poland with a groin injury.
And Lennon said: "Nir and James both went for groin scans on Monday and we think Nir is going to be a bit longer term than Jamesy, and we will need to wait and see what the results of the scans bring back."
On a more positive note for Celtic fans, centre-back Steven Mouyokolo and Swedish defender Mikael Lustig are both nearing returns to first-team action.
Mouyokolo had barely featured for the Glasgow giants before he was struck down with a ruptured Achilles tendon in September while Lustig has been out for four months with a hip injury.
Lennon believes both are well on the road to recovery and will provide a welcome boost as he begins his preparations for next season.
"Steven Mouyokolo is not far away and is out running now," said the Parkhead boss. "Mikeal Lustig will be another three or four weeks and it will be good to have both of them back as they have been two long-term absentees."
The Armagh man also lauded Mouyokolo for his spirit while battling back to fitness.
He said: " He's been terrific, his attitude has been fantastic and the medical team are delighted with the progress he's making.
"He was really disappointed, but the attitude and the character he has shown to come back has been fantastic."