Roma was held to a 1-1 draw at home by lowly Sassuolo after conceding a last-minute equalizer, while AC Milan's struggles continued with a goalless draw at bottom club Chievo Verona in Serie A on Sunday.
Sassuolo defender Alessandro Longhi's own goal looked to have secured victory for Roma. But 19-year-old Domenico Berardi, who scored a hat trick last week, leveled with the last kick of the game.
Roma is four points clear of Juventus and Napoli, which play each other later in Turin.
Milan has picked up just two points in four rounds and coach Massimiliano Allegri's job is very much at risk.
Milan dominated in Verona, where Robinho hit the post twice. Riccardo Montolivo was sent off seven minutes from time and was followed by Chievo substitute Sergio Pellissier in stoppage time.
Lazio's misery also continued as it drew 1-1 at Parma, while high-flying Hellas Verona lost 2-0 at Genoa.
Roma's record start of 11 opening wins was halted by a draw at Torino last week. Sassuolo had started the season badly but had only lost one of its previous four matches.
Sassuolo coach Eusebio Di Francesco was given a warm welcome by the home fans. The former midfielder spent four years at Roma, winning the title in 2001.
Roma took the lead in the 19th minute. Alessandro Florenzi's effort was brilliantly saved by Gianluca Pegolo, but Longhi bundled the rebound into his own net.
Adem Ljajic almost doubled Roma's lead in first-half stoppage time but Pegolo pulled off a fantastic one-handed save.
Sassuolo went close to leveling five minutes from time as Roma goalkeeper Morgan De Sanctis denied Antonio Floro Flores with an outstretched foot.
However, it did snatch a point when Berardi blasted in under the bar following a goalmouth scramble.
Milan had slipped into the bottom half of the table and lost at Barcelona in the Champions League in midweek. On Sunday, it was still without the injured Stephan El Shaarawy, Mattia De Sciglio, Giampaolo Pazzini and Matias Silvestre, while Mario Balotelli was suspended.
Milan dominated but Chievo had the best chance in the first half when Christian Abbiati palmed away Marcelo Estigarribia's effort from under the bar with a fine one-handed save.
Chievo should have taken the lead shortly after the interval but Luca Rigoni fired wide of an open goal following a swift counter attack.
Milan was piling on the pressure and Chievo goalkeeper Christian Puggioni did well to deny Urby Emanuelson and Philippe Mexes
Robinho hit the outside of the post and Milan went even closer 10 minutes from time when the Brazilian again hit the woodwork and his shot rebounded to Kaka, who fired over the bar.
Earlier, Chievo's Alberto Paloschi - who is co-owned by Milan - thought he had scored but his effort was ruled out for a tigh offside decision.
Montolivo was sent off after picking up a second booking, while Pellisier was shown a straight red for dissent.
Lazio had won just one of its past six matches but seemed on course for victory when 18-year-old Keita Balde scored a delightful goal on his Serie A debut. However, Alessandro Lucarelli headed in the equalizer.
Genoa, which has improved since Gian Piero Gasperini took over, earned its fourth win in five matches thanks to goals from Daniele Portanova and Juraj Kucka.
Former Genoa striker Luca Toni headed a free kick off the post for Verona, which had won five of its past six games.
Elsewhere, a pair of Daniele Conti free kicks helped Cagliari to a 2-1 victory over Torino, ending a run of three successive defeats. Ciro Immobile had leveled for Torino.
Marko Livaja scored in stoppage time to snatch a 2-1 win for Atalanta against Bologna.
