Livorno, Bologna and Catania have been relegated from Serie A.
Bottom side Livorno was already all but down and its fate was sealed by a 1-0 loss at home to Fiorentina, which is now guaranteed UEFA Europa League football.
Juan Cuadrado's tap in just before the hour mark decided the match, while the host finished with 10 men after Miguel Borja was shown a red card in stoppage-time.
Catania and Bologna joined it in going down, Catania's 2-1 win at the Stadio Renato Dall'Ara in vain.
Luciano Monzon's first-half opener was cancelled out by Bologna's Archimede Morleo with 10 minutes remaining, but Gonzalo Bergessio grabbed a late winner.
Results elsewhere condemned both sides to the drop, with Chievo triumphing 1-0 at Cagliari and Sassuolo winning 4-2 against Genoa.
Dario Dainelli's second-half winner saved Chievo, while Sassuolo completed a great escape thanks to late strikes from Nicola Sansone and Antonio Floro Flores, his second of the game.
Sassuolo had twice been pegged back by Genoa, Emanuele Calaio and Alberto Gilardino responding to goals from Floro Flores and Davide Biondini, but it dug deep to get over the line.
Champion Juventus moved on to 99 points for the season with a 1-0 win at Roma, substitute Dani Osvaldo with the goal in the fourth minute of stoppage-time.
Torino's 1-1 draw at home to Parma ensured the fight for the final Europa League place would go down to the final day of the season.
Torino remained a point ahead of its opponent and took the lead through Italy's leading scorer Ciro Immobile just before the break
It received another boost when Alessandro Lucarelli was sent off in the 63rd minute, but Jonathan Biabiany brought the 10 men level after Antonio Cassano's penalty was saved.
Immobile also saw red for diving late on.
AC Milan suffered a setback in its bid to qualify for the Europa League as it fell to a last-gasp 2-1 defeat to local rival Atalanta.
An own goal from Gianpaolo Bellini gave the Rossoneri the lead early in the second half, but a second-half penalty from German Denis and a Franco Brienza effort with the last kick of the game turned the match on its head.
The defeat left Milan two points behind Torino.
Finally, Napoli thumped Sampdoria 5-2.
Duvan Zapata put the visitor in front before Lorenzo Insigne made it two. Eder pulled a goal back for the Blucerchiati, but Jose Callejon soon restored Napoli's two-goal advantage.
Marek Hamsik and an own goal from Shkodran Mustafi gave the Azzurri a comfortable lead before Pawel Wszolek grabbed a late consolation.