Two goals by midfielder Andrea Lazzari gave Atalanta a surprise 2-0 home victory over Serie A leaders Juventus in the first leg of their Italian Cup last 16 tie on Friday.
There was also disappointment for AS Roma, whose miserable season continued when a Tore Andre Flo double condemned them to a 2-1 first-led defeat at home to Siena.
Juventus had chosen to rest several key players, including striker Alessandro Del Piero and goalkeeper Gianluigi Buffon, for the game in Bergamo.
They had still been expected to beat Atalanta, who occupy the opposite end of Serie A, but 19-year-old Lazzari tore up the form book in the 58th minute when he beat reserve keeper Antonio Chimenti from a tight angle.
With 15 minutes remaining, Juve midfielder Olivier Kapo skimmed a post but in the next move Lazzari doubled the home side's advantage, latching onto a pass by Igor Budan before firing in off the crossbar.
Roma, who are already out of the Champions League and hang just one point above the Serie A relegation zone, fell behind in the 37th minute when Norwegian striker Flo nodded in Gianluca Falsini's cross at the near post.
Italy international Francesco Totti levelled for the hosts with a superb solo run shortly after the interval.
But four minutes from time Flo took advantage of a defensive mix-up between keeper Gianluca Curci and defender Giuseppe Scurto to head in the winner.
In an earlier match, four-time Cup winners Sampdoria were 2-0 winners over Torino, the only non-Serie A side left in the competition.
In the 77th minute Sampdoria playmaker Cristiano Doni timed his run into the area perfectly to head in a chip by Francesco Flachi.
Striker Vitali Kutuzau sealed victory a minute from the end with a simple tap-in.
Holders Lazio play Cagliari on Sunday.
