The Juventus goalkeeper believes the young Frenchman has the potential to win the Ballon d'Or down the road.
The France international refused to sign a new contract at Old Trafford after becoming frustrated at a lack of first-team opportunities under Sir Alex Ferguson, and left for Turin on a free transfer in the summer of 2012.
Buffon believes the 20-year-old Pogba has the potential to be a future Ballon d'Or candidate and cannot understand why United did so little to keep him.
"I voted for [Andrea] Pirlo, Cristiano Ronaldo and [Lionel] Messi [in the 2013 Ballon d'Or vote]," the Italy skipper told Italia 1. "Pirlo because he is the best in his role, Ronaldo because he was the best in 2013, Messi because he is the best of all time.
"In the future I could vote for Pogba. He is one of those players that leaves you open-mouthed. Myself and my teammates, even in the third or fourth training session with him when he was still a stranger, wondered if they are blind in Manchester."
Buffon has won every honor in the Italian domestic game and was a part of the Italy side that claimed a fourth World Cup title in 2006, but the Champions League trophy has continued to elude the 35-year-old, who came closest to it in a shootout loss to AC Milan in the 2003 final.
With Juve eliminated in the group stage of this season's competition, Buffon doubts whether his team will win the tournament during his time there.
"Compared to big clubs in Europe, there's still a little something lacking," he said. "When we met Bayern Munich last year, I realized that there was something still to be filled. Conte is sure we will win the Champions League. I had this thought 20 years ago but it has certainly began to waver a bit."