The 29-year-old, who spent a fruitless spell with the Nerazzurri several years ago, mentioned during a lengthy interview that Inter were relatively unstable in the late 1990's till the early years of the third millennium.
"When I was at Inter (1998-1999 and then 2000 - January 2001), it was a club that were searching for its identity," the Italian international told FIFA's official website.
He also refereed that La Beneamata had fired a good number of tacticians during that period, which he cited as one reason behind the lack of organization.
"There were a lot of comings and goings and in particular a number of coaches who were relieved of their duties," said Pirlo.
What's more, he assured that the Rosseneri have been much more consistent throughout the last few years.
"AC Milan, on the other hand, have always been a model club in terms of success and also the way it is organized," he added.
"When I was at Inter, they weren't ready to be on the same level as AC Milan."