Celtic's Jozo Simunovic sent to specialist as Nir Bitton misses Rennes trip
Jozo Simunovic has been sent to a specialist and could join Nir Bitton in missing Celtic's Europa League Group E opener away to Rennes on Thursday.
Simunovic has missed Celtic's last three games with a knee problem.
Bitton, who have been filling in at centre-back in his absence, withdrew from international duty with Israel.
Celtic manager Neil Lennon said: "Nir is going to be out for three weeks with a hamstring strain and Mikey Johnston with a groin injury."
Forward Johnston, midfielder Bitton and Simunovic will all miss Saturday's Scottish Premiership trip to face Hamilton Academical.
"The internationals have come back all fit and well," Lennon said. "The only absentees we have are from the fallout from the Rangers game."
Meanwhile, defender Kristoffer Ajer, who withdrew from Norway's squad, and Australia midfielder Tom Rogic have returned to fitness.
Rogic has yet to play this season and Lennon added: "That's a welcome boost, a player of that quality.
"Kris is fit, so he will be in contention. It's great to have that strength in depth."