Sept 18 Genoa and Udinese squandered the chance to provisionally move level on points with second-placed Juventus after defeats by Sassuolo and Chievo Verona respectively in Serie A on Sunday.
Sassuolo followed up Thursday's impressive 3-0 Europa League win over Athletic Bilbao with a 2-0 home victory over visiting Genoa, who were reduced to 10 men in the final minutes.
Matteo Politano put Sassuolo ahead from the penalty spot in the 58th minute and Gregoire Defrel doubled their advantage in the 66th with a diving header.
Genoa's Miguel Veloso was sent off in the 86th and the Portuguese midfielder will miss Wednesday's game at home to Napoli.
Sassuolo's win puts them level with Genoa on six points.
Udinese threw away the lead as they lost 2-1 at home to Chievo after conceding a goal in the fifth minute of added time.
Lucas Castro had grabbed a deserved equaliser for Chievo in the 82nd minute, after Duvan Zapata's diving header had put Udinese on top in the first half, and the Argentine laid on the pass for Fabrizio Cacciatore to tap in the last-gasp winner.
Chievo have seven points with Udinese stuck on six.
Juventus, on nine points, visit Inter Milan in the late game aiming to preserve a 100 percent record and reclaim top spot from Napoli, who have 10 after beating Bologna 3-1 on Saturday.
(Reporting by Richard Martin, editing by Alan Baldwin)