The two teams face off in the first leg of their last 16 clash on Tuesday night before the return leg takes place in the French capital on 6 March.
United go into the game in sensational form, with boss Ole Gunnar Solskjaer racking up 10 wins in 11 games since replacing Jose Mourinho on a caretaker basis in December.
Buffon believes that the turnaround in fortunes for the Red Devils will make the tie a lot closer than was initially expected, with PSG having recently suffered their first league defeat of the season against Lyon.
“Old Trafford is the temple of a great team with a very important history,” he told Sky Italia.
“This tie must be confronted in a serious way and without any regrets. We’ll regret it if our way of playing isn’t expressed in the way that the match demands.
“Football is strange: two months ago, at the time of the draw, everyone thought that PSG would go through.
“Two months later, seeing what has happened with us and the developments at Manchester United, we are at the least on the same level now.
“This makes you understand how strange it is and how certain balances can swap around in the Champions League.”
Buffon could come up against his former Juventus teammate Paul Pogba once again in Manchester.
“Paul is a golden boy, I’m always pleased to see him because he’s an incredible champion,” Buffon said.
“Of course, I hope he can bring me the respect he owes me and that he’s very calm!”
