The hooker has been sidelined with a hairline fracture to his foot that he picked up while on Six Nations duty with Scotland.
Speaking ahead of Glasgow's visit to London to take on Harlequins, Franco Smith told BBC Scotland: "He had a scan about 10 days ago and they found a little hair fracture there in his foot. He played the last game against Ireland with that foot already injured, so it's going to take a while before we see him.
"Six to eight weeks and can be even longer. It is all on how he reacts to treatment that shortens or lengthens the time, which is the same with Huw Jones (who is out with a finger injury)."
Smith also provided an update on Sebastian Cancelliere who was injured in last weekend's game against Scarlets.
He revealed that the winger should be back in a matter of weeks rather than months as it is just a "bone bruise".
Unfortunately for Glasgow fans it will be a while yet before Richie Gray returns to the team sheet as the head coach wants him "in the best form going forward".
"If it's about return to play, then maybe. But if it's about return to form then I think we're still a slight distance away.
"He's an older player now and I don't want to risk injury towards the end of the season, and in that role specifically having JP du Preez already injured.
"Yes, we want him back as soon as we can but not to the detriment of his health. We want him in his best form going forward."