First-half goals from Aleksei Miranchuk and Gianluca Scamacca and a late Teun Koopmeiners strike boosted sixth-placed Atalanta's chances of a spot in Europe's top club competition.
Francesco Calzona's Napoli stay seventh, nine points behind Bologna who are fourth and currently in the final Champions League spot ahead of their home fixture with rock-bottom Salernitana on Easter Monday.
Napoli are also six points behind fifth-placed Roma with the capital club at Lecce and Italy in a good position to get an extra spot in next season's revamped Champions League. "We're not mathematically out of it but the chances of us getting there are very slim," said Calzona after his first league defeat as Napoli boss.
Napoli have 30 fewer points than they had at this stage last season and under Calzona have failed to keep a clean sheet in eight matches. "In certain situations we melt away. We're fragile when we don't have the ball," said Calzona. "We need to find some defensive solidity because it's not good enough."
Both Roma and Bologna have to travel south for matches at the Stadio Diego Armando Maradona before the end of the campaign. Atalanta lurk a point behind Roma with a game in hand and the wind in their sails after a hugely impressive win.
"The next month-and-a-half is very important for us, not dropping points at a ground like this is huge," said goalscorer Scamacca. "Today we put in a perfect performance."
Scamacca's low strike was his first in the league since the end of January but his third in four matches after netting in both legs of Atalanta's Europa League win over Sporting Lisbon.
The 25-year-old is hoping for a spot in Italy's Euro 2024 squad after missing out on the European champions' most recent friendlies. "(Italy
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