Four-time defending champions Juventus crashed out of the Coppa Italia on Wednesday with a 3-0 quarterfinal defeat by Atalanta, as AS Roma suffered a humiliating 7-1 thrashing at the hands of Fiorentina.
Juventus had been bidding for a fifth consecutive league and Cup double this season but a Duvan Zapata brace after Timothy Castagne's opener put the side from Bergamo through to a semi-final meeting with Fiorentina.
Castagne opened the scoring after 37 minutes with Zapata grabbing another two minutes later, before adding a third four minutes from time for his 17th goal in ten matches.
"It's only human not to always be top. Now let's put this behind us and think about the next Serie A match against Parma," said Allegri, who was banished from the touchline for dissent. "I don't know how many games the lads have won. In Rome we had a terrible first half but we fought back. This evening everything went wrong.
"It would have been crazy to think we could win every match. It hurts to go out because we really wanted this trophy."
"Even the most optimistic fan could not have predicted this victory," said coach Gian Piero Gasperini as the side from Bergamo target their second Cup title after 1963.
Earlier in Tuscany Federico Chiesa scored a hattrick as Fiorentina crushed a "shameful" Roma side.
Chiesa scored two early on, adding a third in the second half past overwhelmed Roma goalkeeper Robin Olsen, with Giovanni Simeone bagging a brace in the last ten minutes.
"I'm bitter, but I won't quit," said Roma coach Eusebio Di Francesco. "I'm disappointed in the team, there are no excuses. I struggle to explain what happened, as it was a game we got wrong in every conceivable way. It was shameful."