Teenage forward Domenico Berardi scored his third hat trick of the season to help Sassuolo win 4-3 at high-flying Fiorentina on Tuesday and boost its hopes of Serie A survival.
Berardi scored all his goals in the first half to help lift his club out of the bottom three.
The 19-year-old also netted three times against Sampdoria and scored four against AC Milan in what proved to be Massimiliano Allegri's final match in charge.
Italy forward Giuseppe Rossi made his first league appearance since Jan. 5 and marked his return from injury with a goal which almost inspired Fiorentina to an astonishing comeback.
The New Jersey-born forward will have boosted his chances of making Italy's World Cup squad.
Fiorentina remained fourth while Sassuolo moved two points and two places above the drop zone.
Napoli comfortably beat 10-man Cagliari 3-0 in the late match.
Fiorentina goalkeeper Antonio Rosati was making his Serie A debut and he pulled off a couple of decent saves before Sassuolo opened the scoring with a 23rd-minute penalty following a handball by Borja Valero.
Berardi doubled his tally nine minutes later, collecting Nicola Sansone's threaded pass before firing in at the near post. Rosati got a hand to the ball but couldn't prevent it from squirming through.
Big 1st impression
The on-loan Juventus forward completed his hat trick three minutes from halftime with his 16th goal in his debut Serie A season.
Substitute Joaquin was introduced early in the second half for Fiorentina and he had an immediate impact, winning the penalty which Gonzalo Rodriguez converted.
Sansone restored Sassuolo's three-goal advantage before Rossi came on in the 65th minute and scored seven minutes later after a swift one-two with Valero.
Coincidentally, Rossi's last goal came against Sassuolo.
Juan Cuadrado reduced the deficit still further 15 minutes from time and Sassuolo goalkeeper Gianluca Pegolo pulled off a stunning save to prevent Rossi from getting the equalizer, while Valero had a strike ruled out for offside deep in stoppage time.
Fiorentina's defeat mathematically assured Napoli of third spot and the final Champions League berth but the newly-crowned Italian up champion was keen to celebrate in style.
The cup was paraded before kickoffm though there was muted celebration as thoughts were with Ciro Esposito, the fan injured in the violence before Saturday's match. There were banners in support of Esposito, who remains in critical condition.
Dries Mertens broke the deadlock with a penalty on his 27th birthday and Goran Pandev doubled Napoli's advantage shortly before halftime.
Marek Hamsik thumped a second penalty against the crossbar after Pandev had been fouled by Marco Silvestri. The goalkeeper was dismissed in that incident, leaving Cagliari at a numerical disadvantage for more than half an hour.
Napoli did score a third two minutes later when Blerim Dzemaili tapped in a rebound after Vlada Avramov could only parry Pandev's effort.