Seven-time European champions AC Milan were shocked by minnows Monza as the hosts scored twice in a frantic finish.
Milan, who had Luka Jovic sent off, fought back from 2-0 down thanks to Olivier Giroud’s volley and Christian Pulisic’s 88th-minute strike.
But goals in added time from Warren Bondo and Lorenzo Colombo gave Monza their first Serie A win over Milan.
Matteo Pessina opened the scoring with a penalty before Dany Mota made it 2-0 just before half-time.
The shock defeat to the small club on the north-eastern outskirts of Milan means Stefano Pioli’s side stay third, two points behind second-placed Juventus and 11 adrift of leaders Inter.
Inter beat Salernitana 4-0 on Friday while Juventus dropped two points in a 2-2 draw at Verona on Saturday.
Elsewhere in Serie A on Sunday there were mixed fortunes for the two Rome sides as Roma won 3-0 at Frosinone but Lazio were beaten 2-1 at home by Bologna.
Milan are next in action on Thursday when they play the second leg of their Europa League knockout play-off against Rennes after a 3-0 win at home in the first leg.
Unless Milan suffer a heavy defeat on Thursday, they will move into the last 16 of the tournament – with Liverpool, West Ham United and Brighton among their potential opponents in the next round.
