Lazio stayed in the hunt by winning 2-0 at Atalanta and Fabrizio Miccoli scored a hat-trick as Palermo were held 4-4 at home to Chievo in a match during which both sides squandered two-goal leads.
Antonio Di Natale and Antonio Floro Flores scored in each half for Udinese against opponents who had Juraj Kucka and Rodrigo Palacio both sent off before halftime.
Udinese moved into third place, which would earn them a place in the final round of the Champions League qualifying competition, with 61 points from 37 games, one ahead of Lazio and three ahead of Napoli.
Libor Kozan and Lorik Cana scored to give Lazio the points at Atalanta while goals from Alessandro Diamanti and Matteo Rubin sank Napoli.
Leaders Juventus (78 points) were away to Cagliari later on Sunday (1845) with second-placed AC Milan (77) involved in the derby against Inter.
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