The former Celtic defender expects the 27-year-old to leave in January or next summer after struggling for game time this season.

Ralston, out of contract next summer, has only managed three cameo appearances this term. The emergence of 20-year-old Colby Donovan has left the Scotland international on the fringes.

Discussing Donovan's new deal on Go Radio, Mulgrew said: "He has earned it. He has shown a great desire to be a Celtic player. He was third choice right-back at one point, and now he has stepped up from nowhere.

"He’ll now be getting wages that he deserves. I would imagine that Ralston will move on either in January or in the summer window based on that.

"But fair play to Donovan."

Donovan has been a staple in the team this season, featuring in all 17 games and starting 15, while Ralston is yet to make a domestic appearance.

His only minutes so far have been brief appearances in the two legs against LASK and the Europa League defeat to Ferencvaros.