Benatia, 29, featured just 14 times in the Bundesliga under Guardiola at Bayern last season before moving to Juve in the summer.
While wearing the Azzurri shirt of Napoli last season, Higuain, 28, failed to beat Milan goalkeeper Donnarumma in two meetings.
"It's a defeat for Italian football," Buffon said. "Of Italy as a country, of the traditions, of everything."
Crotone have been cleared to play their first true home match in Serie A against Napoli on Sunday.
Despite their youth, Milan has started the season remarkably well under Vincenzo Montella but Saturday face their toughest test yet against Juventus.
New owners, fresh investment, a new lease on life and a young, hungry squad: Vincenzo Montella and AC Milan have a bright future ahead.