Pogba, 19, made just seven senior appearances for the Red Devils but was viewed as a rising star and a likely first-team regular.
The French midfielder's contract expired this summer but, despite persistent speculation over his future last season, United were keen to extend his stay and offered him fresh terms as well as the chance for great first-team opportunities next season.
But a long-mooted move to Turin now looks set to happen, although the deal has not yet been confirmed by the Italian champions.
Ferguson made little attempt to hide his displeasure at Pogba's decision.
"Pogba signed for Juventus a long time ago as far as we're aware," he told MUTV. "(It) is disappointing. I don't think he showed us any respect at all, to be honest," he said.
"I'm quite happy that if they carry on that way, they're probably better doing it away from us."
Pogba arrived at United from Le Havre in 2009 - a move that infuriated the French side at the time.
His seven United appearances all came last season and all from the bench.
Three of those were in the Barclays Premier League and three in the Carling Cup, with a solitary Europa League match in a 2-1 defeat to Athletic Bilbao.
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