Napoli's dream of winning the Serie A title lies in tatters after they were humbled 3-0 by a Giovanni Simeone-inspired Fiorentina.
A famous victory at leaders Juventus last weekend had closed the gap to a single point, but the Bianconeri won 3-2 at Inter Milan in dramatic fashion on Saturday to pull clear once again.
Napoli could not keep step with their Scudetto rivals from Turin as, after Kalidou Koulibaly was sent off for fouling Simeone, the Argentine scored a hat-trick to lift La Viola to a first win in four.
The son of Atletico Madrid boss Diego drove Cristiano Biraghi's through ball beyond Pepe Reina in the 34th minute and later doubled up when Milan Badelj's headed attempt rebounded to his feet.
Simeone compounded Napoli's woe with a killer blow from a Federico Chiesa pass deep into second-half stoppage time.
SPAL pushed their relegation rivals Hellas Verona ever closer to the trapdoor by winning 3-1 at the Stadio Marc'Antonio Bentegodi.
Verona's Mattia Valoti turned in Bruno Petkovic's splendid assist in the 13th minute but Mohamed Fares' own goal deep into first-half stoppage time burst the Hellas bubble.
SPAL grew in confidence after the break, with Felipe firing them ahead with 71 minutes on the clock and Jasmin Kurtic rubbing salt in the wound at the death.
With just three games remaining Verona are seven points from safety and next face a trip to AC Milan.
The Rossoneri were 2-1 winners on Sunday after they resisted a late Bologna rally while a video assistant referee call also went their way.
Hakan Calhanoglu stuck Patrick Cutrone's pass away early on at the Renato Dall'Ara but, before half-time, Riccardo Orsolini scored what he thought was a Bologna equaliser - the VAR would rule Rodrigo Palacio had handled the ball. Giacomo Bonaventura then doubled Milan's lead heading into the interval.
Gennaro Gattuso's men twice hit the frame of the goal in their pursuit of a third to kill the game off and they were therefore rattled when Sebastien De Maio halved the deficit with 16 minutes remaining.
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In the early game, Marcello Trotta scored a brace against his parent club as Crotone edged towards safety with a thumping 4-1 victory over Sassuolo.
Former Fulham and Brentford striker Trotta grabbed a first-half double, with Simy also netting twice.
Domenico Berardi notched from the penalty spot for Sassuolo but Crotone moved three points above the bottom three as a result.
Bacary Sagna left it late to rescue a point for relegated Benevento from a 3-3 draw with Udinese.
The former Manchester City full-back was a high-profile signing in February and has helped reinvigorate the Witches, who have nevertheless already taken the plunge back into Serie B.
A topsy-turvy clash saw Udinese's Silvan Widmer and Benevento's Nicola Viola exchange goals before Danilo Cataldi was dismissed for the southerners.
Massimo Coda stuck away a spot-kick to give Benevento the lead but Kevin Lasagna plundered a quick-fire brace before Sagna made his contribution with seconds left.
Elsewhere, Atalanta strengthened their claim on a Europa League spot by dispatching Genoa 3-1, Musa Barrow, Bryan Cristante and Josip Ilicic scoring before Miguel Veloso replied for the Rossoblu.
Veteran striker Fabio Quagliarella scored but would later miss a penalty to forego his 20th goal of the season as Sampdoria downed struggling Cagliari 4-1 at the Marassi.
Dennis Praet, Quagliarella and Dawid Kownacki ensured Samp were cruising come half-time, even though the oldest of their number managed to a hit a post from a spot-kick.
Cagliari attempted to fight back as Leonardo Pavoletti notched but Luca Cigarini's sending-off ended their challenge before Gaston Ramirez added gloss to the scoreline for Samp.
In the late game, Sergej Milinkovic-Savic scored before the hour as Lazio triumphed 1-0 at Torino.
The Biancocelesti could have taken the lead in the first half but Luis Alberto's penalty was saved.
Despite their win, Lazio will be concerned about the league's top scorer Ciro Immobile, who was withdrawn injured after 15 minutes.