Inter Milan have a new star player - with a familiar name in Serie A - as Marcus Thuram helped the Nerazzurri beat fierce rival AC Milan 5-1 in a derby match to maintain their perfect start to the season.
Thuram scored a superb goal to double Inter's lead shortly before halftime, having had a significant hand in the fifth-minute opener. That was netted by Henrikh Mkhitaryan, who also scored Inter's third after Rafael Leão had got Milan back into the game amid a torrential downpour at San Siro on Saturday.
Former Milan midfielder Hakan Çalhanoğlu added a penalty 11 minutes from time and Davide Frattesi capped a great night for Inter in stoppage time.
It was Thuram's second Inter goal in as many matches. He also has three assists in his four matches since joining on a free transfer from Borussia Mönchengladbach.
Inter are now the only team to have won their four opening matches and the Nerazzurri moved two points ahead of Juventus, who beat Lazio 3-1 earlier. Milan are three points behind Inter.
Milan have now lost their last five derbies and this latest defeat to Inter was their heaviest against their bitter rivals in 14 years. However, Rossoneri coach Stefano Pioli said his team had no need to apologise.
The Milan teams were the only ones with maximum points in Serie A coming into the Derby della Madonnina.
Thuram got on the scoresheet himself in the 38th minute when collected an overhit pass from Denzel Dumfries on the left side, cut past Thiaw and curled a sensational strike into the top right corner.
Milan managed to get back into the match 12 minutes after the break as Leão slotted home an inspired pass from Olivier Giroud. It was the first time Inter had conceded this season.
However, Inter restored their two-goal advantage in the 69th when Mkhitaryan finished off a good team move and the Nerazzurri sealed the result when Çalhanoğlu blasted home a penalty.
Frattesi, who scored two goals for Italy against Ukraine in the same stadium on Tuesday, capped a great week with his first Inter goal.
Rudi Garcia's substitutions helped Napoli avoid a second successive loss.
Matteo Politano was brought on at halftime and Giacomo Raspadori 13 minutes later. Raspadori gave Napoli a chance of rescuing a point when he netted in the 76th minute, and Politano volleyed in the equaliser with six minutes remaining.
Dušan Vlahović struck twice to help ensure a convincing win for Juventus.
Luis Alberto pulled one back for Lazio in the 64th but Vlahović doubled his tally three minutes later with a fantastic solo effort as he chested down Weston McKennie's long ball and fired into the far bottom corner.
Juventus remained unbeaten while it was Lazio's third loss.