The Rossoneri have been rocked by a number of injuries in midfield but the former Cagliari boss is adamant that the club was right to let the Italy playmaker go.
The Rossoneri are currently desperately short on bodies in the middle of the park, with the club having confirmed on Sunday evening that Alexander Merkel will be unavailable for two months and has joined Alberto Aquilani, Kevin-Prince Boateng and Gennaro Gattuso on the sidelines.
The injury crisis has prompted many to once again question the wisdom of the decision to part company with Pirlo, who has played a key role in Juve's revival this term.
However, Allegri, speaking after Sunday night's 3-0 victory over Cagliari, told Sky Sport Italia that the club had made the right call.
"Pirlo is a champion and is having a great season," he acknowledged. "It was a choice, which included economic factors, for us to part.
"Teams win with champions but some teams also win after they're sold."
And while the transfer window does not close for another two days, Allegri claimed that Milan does not need strengthen in midfield.
"No, I would not say so," he said when asked about the possibility of new arrivals in the engine room.
"I am not worried about the situation because [Urby] Emanuelson played a good game tonight, not least because his [physical] condition is improving.
"However, I am disappointed that Merkel will be out for two months."
Meanwhile, Allegri admitted that it was vital for Milan to have picked up three points against Cagliari, with Juventus having defeated third-placed Udinese on Saturday night.
"At this time the table has stretched out and it was it was important for us to win to stay in Juve's slipstream and now allow them to pull clear," he reasoned.
Milan remains second in Serie A, one point behind the Bianconeri but five clear of Udinese.