Neither Vasilis Barkas or Scott Bain have been able to establish themselves as the Hoops’ undisputed number one in recent times, and reports have suggested that Ange Postecoglou is on the lookout for a new goalkeeper this summer, with Joe Hart touted as a potential target.
Gordon left Parkhead to return to Hearts last year, and has shone for his boyhood club ever since.
Writing in a column for The Scottish Sun, Stewart argued that the Bhoys had made a big mistake by letting him go.
He said: “What Ange Postecoglou would do for someone like Craig Gordon right now.
“A goalkeeper the Celtic boss could actually rely on, a safe pair of hands amid the storm.
“Instead, Gordon will be in the opposite goal for Hearts against the Hoops because they let him go.
“And if anything sums up the mess they’re in, it’s that very decision.
“Put simply, they blew it when they chose not to offer him a contract last year. Let’s face it, it’s not as if the big man would have been that difficult to deal with.
“It wouldn’t have cost the earth to keep him. But instead they were content to let him walk — and spend big on Vasilis Barkas instead.
“I’ll let you do the maths on that one. And their loss has gone on to become Hearts’ gain.”
Gordon is expected to start between the sticks when Hearts host Celtic at Tynecastle on Saturday evening.