Harper spent almost two decades at Newcastle and believes Bruce rues the day he turned down the Toon job.
"Although we haven't discussed it, I think he probably regrets not taking that opportunity that presented itself," said the keeper.
"You can probably understand his reservations at the time, following on from such an iconic, legendary man as Sir Bobby.
"As time has gone he probably realises - especially with supporting the club as a boy - what a fantastic opportunity that was. Who knows in the future?"
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