In a wide-ranging hour-long interview with US TV network PBS, Ferguson, who left United in the summer after almost 27 years in charge, revealed he was asked to manage Chelsea not long after Russian Roman Abramovich bought the club in 2003.
"They used an agent to approach me when Abramovich first took over the club," the Scot said. "And I said, 'No chance'. I always come back to this point - why would you leave?"
Harris wondered why Ferguson chose now, after successor David Moyes' challenging start at Old Trafford, to reveal the approach.
"Why bring it out now?" Harris told Press Association Sport. "They haven't started the season off particularly well. Maybe he's trying to upset the apple cart.
"If it was true, I'd have thought it would've leaked out before.
"It just seems strange now all of a sudden since he's retired it's come to light."
It is the first time Ferguson has commented publicly on the matter, although it was previously reported by the Manchester Evening News.
It was not a shock to Chelsea Supporters' Group chair Trizia Fiorellino.
"I'm not surprised at all; I'd have been surprised if he wasn't offered the job," she said.
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