Juventus, chasing a 10th straight Scudetto, won 2-0 earlier Sunday to move seven points behind leader AC Milan with a game in hand.
AC Milan held onto top spot on Sunday despite falling to a 3-0 home defeat by Atalanta, while second-placed Inter settled for a goalless draw at Udinese.
Napoli missed the chance to move ahead of Juventus and sit sixth, two points adrift of the Champions League berths, equal on 34 points with Lazio who beat European rivals Sassuolo 2-1.
"We have only ourselves to blame," lamented Napoli coach Gennaro Gattuso.
"If you score and then at the first opportunity you fall apart, that's not good.
"We want to return to the Champions League but we can't if we perform like this."
Gattuso's side got off to a perfect start in Verona as, almost straight from kick-off, Mexican forward Lozano fired home Napoli's fastest-ever Serie A goal after Verona defender Federico Dimarco missed Diego Demme's long ball.
But Dimarco made up for his mistake by volleying in the equaliser on 34 minutes for eighth-placed Verona.
Antonin Barak put Verona ahead shortly after the hour mark with a low finish into the far corner from a tight angle, before Mattia Zaccagni headed in the third with 11 minutes to go.
Napoli's record scorer Dries Mertens and Nigerian striker Victor Osimhen, who returned after recovering from a shoulder injury and coronavirus, came off the bench in the second half but failed to inspire a comeback.
Napoli are now equal on points with Lazio who rallied past Sassuolo, to stretch their winning streak to four games.
Francesco Caputo found the back of the net for the visitors after six minutes in the Stadio Olimpico before Sergej Milinkovic-Savic pulled the hosts level with a powerful 25th-minute header.
Ciro Immobile scored the winner with 19 minutes to go for his 13th goal this campaign.