Beckham will join up with the Italian side on a six-month loan from the LA Galaxy and will feature from January onwards, while Milan take on the Red Devils in the Round of 16 of the Champions League.
"You could see Beckham come off the bench to score a freekick at Old Trafford. That is his kind of mentality," the Italian international explained to the People newspaper.
"Knowing David, he would not celebrate if he scored. He has too much class."
The 'Spice Boy' also spent a loan period with the Rossoneri last season and Pirlo is convinced that he will be a positive influence again.
"Beckham is among the top five players in the world and has demonstrated that at both club and international level," he concluded.
The 34-year-old made 18 appearances in Serie A in 2008-09.
Adam Scime, Goal.com