The Northern Irishman infuriated the Bhoys support by abandoning the club late in the season, with an unprecedented third consecutive domestic treble still to play for.
Celtic fans unveiled a banner during their game against Hearts last week that read: “You traded immortality for mediocrity. Never a Celt. Always a fraud.”
Mourinho backed the former Liverpool manager’s decision to leave Scotland for a return to the Premier League, but insists he should have finished the job at Celtic Park first.
“If you are asking whether I am surprised at the move, I would say no,” Mourinho told BeIn Sports.
“With all due respect, the Scottish Premiership is not the same as the Premier League. Celtic is a giant club, but the Premier League is big.
“If I were in his position, I would take Leicester’s offer of arriving now, and I would say ‘I want to come to you, but not now.’
“He should have stayed in Scotland and become a champion again – leaving in the right moment.”
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