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The Canadian, 28, made his first appearance for the club since early August, when he was forced off during Celtic’s meeting with Kilmarnock.
Johnston returned to action from the bench, replacing Colby Donovan as he made his long-awaited comeback. However, his return was cut short when he was substituted himself later in the match.
Cameron Carter-Vickers came on to replace the full-back, leaving questions over Johnston’s fitness once again.
The reason for his withdrawal remains unclear, with Celtic yet to establish whether the change was precautionary or the result of a fresh injury setback.
Having only just returned to action, Johnston will be hoping to avoid another spell on the sidelines as Celtic await further clarity on the defender’s condition.