Del Piero, 37, will almost certainly depart Juve this summer after nearly two decades at the club, and Matterazzi has blasted the club's decision not to hand him a new deal.
"It does not surprise me. Gratitude in football has been dead for years. I think Alex could spend 20 years at the club, which would be a historic achievement, but Juve's directors have been clear and Del Piero is not stupid," Materazzi told Sky Sport Italia.
Del Piero made his 700th appearance for the Bianconeri last week.