Atalanta came from behind to beat AC Milan 2-1 in Bergamo on Wednesday and move up to sixth place in the Italian Serie A.
The European champions struck first when Atalanta's Cristiano Doni deflected a Gennaro Gattuso volley into his own net in the 16th minute.
Brazilian striker Pato fluffed a great chance when alone in front of Atalanta keeper Ferdinando Coppola before Antonio Langella threw off two defenders with some smart control and drove in the equaliser three minutes before the break.
Fernando Tissone slotted in the winner in the 68th after Simone Inzaghi had drawn Milan keeper Zeljko Kalac off his line and served the Argentine midfielder.
Milan substitute Ronaldo blasted into Coppola from a good position, Tissone hit the crossbar with a shot from the edge of the area and Coppola denied Clarence Seedorf in stoppage time.
The defeat is a blow to Milan's bid to recover from a poor start and reach the top four to qualify for the Champions League.
They dropped to 10th with 24 points from 17 games and remain 25 points behind leaders Inter Milan after playing the first of three games in hand.
Atalanta's first win in six games gives them 25 points from 19 games and lifts them above Sampdoria, Genoa and Palermo into sixth on goal difference.
Wednesday's game was played behind closed doors after the original match in November was abandoned early on when home fans tried to smash a perimeter fence in protest at the shooting dead of a Lazio supporter by police.
The Bergamo side are playing in difficult circumstances at the moment as club president Ivan Ruggeri is critically ill in hospital after suffering a brain haemorrhage last week.
