Pirlo hailed as title difference for Juventus
Juve are three points clear of Pirlo's former club AC Milan at the top of the table.
"Pirlo is their extra man," Colomba told Sport Italia. "He is a player who has allowed the others around him to grow.
"I think that has made the real difference this season.
"Juventus are now a very strong team mentally - they are aware that they are good physically and technically."