Charlie Mulgrew believes Anthony Ralston could leave Celtic in January or next summer after Colby Donovan signed a new long-term contract.

Celtic confirmed on Monday evening that Donovan has committed his future to the club until 2031, rewarding his emergence as an important first-team player.

The academy graduate has made 17 appearances this season, including 15 starts, and earned his first senior Scotland call-up during the recent international break.

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His progress has made Ralston’s route into the team considerably more difficult.

Once the familiar alternative to Alistair Johnston, Ralston has slipped behind Donovan and is now struggling even to make domestic matchday squads.

Mulgrew believes Monday’s announcement could point towards a departure.

He said on Go Radio: “You’d imagine Ralston probably move on, you’d imagine based on that either January or the summer window.”

Ralston’s lack of involvement explains why his future is becoming a talking point.

He has yet to play a domestic match for Celtic this season. His three appearances have come in Europe, against LASK in both legs of the Champions League play-off and Ferencváros in the Europa League.

His most recent Premiership bench appearance was against Rangers on September 20, having also been an unused substitute against Aberdeen earlier that month.

Those are limited opportunities for an experienced player who previously provided dependable cover at right-back.

Donovan’s new deal reinforces Celtic’s commitment to his development. It also leaves Ralston facing a difficult question about where regular football might come from.

Johnston’s fitness will influence Celtic’s immediate defensive requirements, but Ralston has struggled for minutes even during the Canadian’s absence.

Unless that changes, Mulgrew’s prediction is easy to understand. A player who once regularly stepped in is now watching another academy graduate take those opportunities.