There's a chance he'll make it back from injury to face off against Bayer Leverkusen on Thursday night in the Europa League.
But Callum McGregor could easily have been playing against the German giants in the BUNDESLIGA.
That's according to former Celtic midfielder Mark Fotheringham, who began his career at Parkhead before then playing alongside the current captain during his loan spell at Notts County.
He's revealed McGregor, who penned a new five-year deal to stay at Celtic last week, was the subject of transfer interest from Hertha Berlin.
Speaking to the Scottish Sun, Fotheringham said: "Callum’s a massively important player for Celtic.
"Bayer will be delighted if he’s not involved on Thursday night. Clubs in Germany are well aware of Callum.
"I know Hertha Berlin were very keen on him at one stage.
"I’m very concerned for Celtic without Callum. Him being out has highlighted how important he is to everything.
"They lack that football brain on the pitch.
"He’s a coach on the pitch. The manager can get messages to him and he’ll relay it to the rest of the players."
Fotheringham also paid McGregor the ultimate Celtic compliment – insisting he's the 21st-century incarnation of Paul McStay for his commitment months after former captain Scott Brown left the club.
He added: "When I was a kid, Paul McStay was my big hero. The Maestro. Now I see Callum the same way. He’s the new Maestro.
"In 20 years from now there will be supporters talking about him the same as fans currently talk about McStay.
“Bayer will be formidable opposition for Celtic. The boy Wirtz looks absolute class and has an incredible future.
“But as far as I’m concerned, Callum’s the same for Celtic.”
