Napoli's title hopes looked in tatters on Sunday after a shock 3-0 defeat at Fiorentina, complete with an early sending-off for Kalidou Koulibaly and a hat-trick from Giovanni Simeone, edged Juventus closer to a seventh successive Serie A title.
With just three games left, Juventus have a four-point lead on closest challengers Napoli and could wrap up yet another 'Scudetto' next weekend.
Argentina forward Simeone -- the son of Atletico Madrid boss Diego Simeone -- scored all three goals in a spectacular display to keep Fiorentina's Europa League hopes alive.
Koulibaly, labelled a hero when he scored the last-gasp header that kept Napoli's ambitions alive with a 1-0 win over Juventus in Turin last week, turned villain in Florence when he was sent off after just eight minutes.
"We lost tactical certainties after the sending off, and faced with adversity we lost our way and our nerve too," said Napoli coach Maurizio Sarri.
"The entire team had a bad performance. We won as a team at other times, today we lost as a team. I didn't see any positives."
Juventus battled past 10-man Inter Milan in a San Siro thriller on Saturday to prevail 3-2 thanks to two late goals in three minutes.
Massimiliano Allegri's champions host Bologna on Saturday and will be assured of the title if they win and Napoli lose at home against Torino on Sunday.
"I want the whole team to fight back straight away," said Sarri as Napoli chase a third title after 1987 and 1990. "If we always focus on the next game, we can have a good season."
Napoli never recovered from Koulibaly's dismissal, the towering Sengalese defender initially shown a yellow card for kicking out at Simeone as he charged towards goal.
But a video assistant referee (VAR) review at the Stadio Franchi upgraded the yellow to red, with a free-kick given instead of a penalty.
Sarri replaced midfielder Jorginho with central defender Lorenzo Tonelli.
But Napoli struggled to contain their rivals, Simeone breaking the deadlock by firing through the legs of goalkeeper Pepe Reina after 34 minutes.
Simeone pounced to drive home the second on 62 minutes after the ball initially bounced off Elseid Hysaj and Reina saved with his leg.
The 22-year-old completed his hat-trick three minutes into injury-time to claim his 13th goal this season.
- Champions League suspense -
The suspense remains over who will join Juventus and Napoli in the Champions League next season.
Both Roman clubs occupy the two remaining places with Roma beating Chievo 4-1 and Lazio edging past Torino 1-0 to remain third and fourth respectively level on points, with Inter Milan four points behind in fifth.
Luis Alberto saw his penalty saved and Serie A top-scorer Ciro Immobile went off injured, with Sergej Milinkovic-Savic's header giving Lazio all three points at Torino.
The final game of the season will see Lazio host Inter.
AC Milan maintained their Europa League hopes with a 2-1 win at Bologna to end a six-game winless streak including last week's shock reverse to bottom club Benevento.
First-half goals from Hakan Calhanoglu and Giacomo Bonaventura ensured Milan -- one point behind sixth-placed Atalanta, who beat Genoa 3-1 -- keep touch with the Europa League places.
Sampdoria and Fiorentina are three points behind Milan.
In the relegation battle, SPAL moved out of the bottom three with a 3-1 win against Verona, who now look destined for the drop.
A late Bacary Sagna goal grabbed a 3-3 draw for Benevento against Udinese, who had looked set to earn a first win under new coach Igor Tudor after a 12-match losing streak cost predecessor Massimo Oddo his job during the week.
Chievo, whose coach Rolando Maran was fired on Sunday, drop into the relegation zone with just three games to play.
Meanwhile, Marcello Trotta and Nigerian forward Simy scored a brace each as Crotone beat Sassuolo 4-1 to move away from the drop zone.
Don't look now: Napoli's Spanish forward Jose Callejon reacts as he leaves the field after the 3-0 defeat