A controversial goal led to Inter Milan's first defeat of the season in a 3-1 loss at Lazio in Serie A. (More Football News)
Felipe Anderson scored a late winner while Inter fullback Federico Dimarco was down injured.
The goal on Saturday infuriated Inter but the rules say the referee should interrupt play only when there is a risk of serious injury, which was not the case.
Inter's players were calling for Lazio to kick the ball out of play when Anderson redirected a rebound of a shot from Ciro Immobile.
Sergej Milinkovic-Savic then secured the three points for Lazio with a header in stoppage time as Inter's focus was lost.
Immobile had canceled out Ivan Perišic's first-half penalty with a penalty of his own.
It marked a bitter return to the Stadio Olimpico for new Inter Milan coach Simone Inzaghi, who coached Lazio for the last five seasons after also spending the bulk of his playing career with the Roman club.
Inzaghi acknowledged, “We lost our heads.
“That shouldn't happen, because the referee can let play continue and there were 10 minutes plus stoppages to go. We should've kept playing.”
Inter remained in third place but dropped five points behind city rival AC Milan, which came back from two goals down for a 3-2 win over Hellas Verona at the San Siro.
Napoli can reclaim the lead on Sunday if its beats Torino to extend its perfect start.
Lazio, which moved up to fifth, had been slow to adapt to Maurizio Sarri's fast-paced attacking game but beat Roma in the city derby late last month and is developing into a tricky opponent.
“Inter had the ball when Dimarco went down, so if someone should have kicked it out it was them,” Sarri said. “There's not much to debate. They attempted to score with a man down then we continued to play.”
AC MILAN COMEBACK
An own goal from Koray Günter completed Milan's comeback in the 3-2 win over Verona.
After Gianluca Caprari and Antonin Barak put Verona ahead 2-0 after 24 minutes, Olivier Giroud pulled one back with a header near the hour mark, Franck Kessie converted a penalty and then Günter redirected a cross into his own goal.
The winner came just after Zlatan Ibrahimovic came on to mark his return from injury. However, fellow center forward Ante Rebic came off with a physical problem during the first half.
Earlier, Ukraine midfielder Viktor Kovalenko — on loan from Atalanta — set up one goal then scored the winner as Spezia came from a goal down to beat Salernitana 2-1 and climb out of the drop zone.
It's the first Serie A weekend in the pandemic when stadium capacities have been raised to 75%.