Alistair Johnston had been on the pitch for just 21 minutes against Hibs when Celtic were forced into another substitution.

The Canadian replaced Colby Donovan in the 52nd minute but was heading back off by the 73rd, with Cameron Carter-Vickers taking Johnston’s place.

Neil Lennon questions Celtic staff over Alistair Johnston injury

Speaking on Sky Sports Scotland, Lennon wanted to know why Johnston had been cleared to play when his comeback ended so quickly.

Lennon said: “Well, I don’t understand it. I mean this isn’t the first time this has happened to Alistair. So I don’t know what’s going on behind the scenes.

“Obviously, you know, the medical team and the fitness team and the coaching team have felt that he’s fit to play some part in the game, but quite clearly that’s not been the case.”

Lennon also dismissed the suggestion that Johnston could simply be worried about aggravating his previous injury.

He continued: “I doubt it’s a psychological thing knowing Alistair Johnston’s obviously feeling something. But it’s not right, and I don’t know if he needs a prolonged period.

“Hamstrings are such a difficult injury to recover from. If you don’t get the rehabilitation right and the time right, you can do it again.

“And if this is a reoccurrence of the same injury, that’s a real, real worry for the player.”

Lennon doesn’t know what happened during Johnston’s rehabilitation, and neither do Celtic supporters but his criticism of the decision to bring the defender back was scathing.

Alistair Johnston’s last two Celtic comebacks have lasted just 47 minutes combined

Remember what happened against Sturm Graz last October? Johnston was making his first appearance since picking up a hamstring injury against Kairat Almaty when he pulled up after just 26 minutes.

He didn’t kick another ball competitively for Celtic until April, missing more than five months of football.

On Sunday, Johnston managed 21 minutes against Hibs. That’s 47 minutes across two comeback appearances, and the first ended with him spending another five months on the treatment table.

Following the Easter Road win, Martin O’Neill admitted he was concerned about Johnston but couldn’t confirm whether the defender had aggravated his hamstring.

The Celtic manager explained that Johnston felt discomfort higher up the muscle than before. He’s hoping it might only be cramp, with scans needed to find out exactly what happened.

Johnston has already lost a huge chunk of his Celtic career to hamstring problems. The last thing he needs is another lengthy spell watching from the sidelines, especially after working his way back into contention.

And while Lennon cannot know everything that went into the decision to play Johnston, Celtic will have some serious questions to answer if the scans confirm another injury.