Genoa ended Lazio's perfect start to the season thanks to a goal from former Roma striker Marco Borriello, despite an otherwise one-sided game at the Stadio Olimpico.
Lazio, who left Miroslav Klose on the bench, dominated most of the game but were restricted to long-distance efforts by a disciplined Genoa defence.
Borriello struck on the counter-attack in the 79th minute to condemn Lazio to their first defeat and lift the Rossoblu into the top half of the table.
Vladimir Petkovic decided to give Klose a rest in view of the upcoming midweek fixtures in Serie A, but by choosing Libor Kozak and Mauro Zarate in his attack, he lacked a cutting edge.
Indeed, the closest the Biancoceleste came to opening the scoring came from long-range shots from Hernanes and Antonio Candreva.
Sampdoria's 100% record in Serie A was brought to an end by Torino, who earned a point at the Stadio Luigi Ferraris thanks to a 1-1 draw on Sunday.
Both goals came from the penalty spot in Genoa with Rolando Bianchi scoring first for Torino in the 69th minute before Nicola Pozzi replied five minutes from time.
Torino goalkeeper Jean Francois Gillet then took centre stage to preserve a point for his side as the hosts surged forwards in search of a winner which they could not find for the first time this season.
Cristian Raimondi denied Gian Piero Gasperini any joy on his debut as Palermo manager with his late header earning Atalanta a 1-0 victory.
The former Inter Milan boss replaced Giuseppe Sannino at the Renzo Barbera following the Sicilians' winless start to the season, but the barren patch will extend to Wednesday night's trip to Pescara at the earliest.
For Stefano Colantuono's Atalanta, though, it was a second consecutive league win and their first home triumph of the new campaign.
Napoli dropped their first points of the season as they were held to a goalless draw at Catania - despite playing for virtually the entire match against 10 men.
The hosts had defender Pablo Alvarez sent off after only two minutes for a last-man foul on Edinson Cavani at the Stadio Angelo Massimino, but the visitors were unable to find the breakthrough.
The result left Walter Mazzarri's side two points behind leaders Juventus and saw Catania slip to eighth.
It was a tale of three penalties as 10-man Parma salvaged a last-gasp 1-1 draw against Fiorentina on Saturday.
Fiorentina's new Argentinian defender Facundo Roncaglia scored his first goal in Italy with a stunning first-half strike before Jaime Valdes missed the chance to level from the penalty spot.
Aleandro Rosi received his marching orders for the home side two minutes from time, only for Stevan Jovetic to miss the resulting penalty.
Parma withstood a heavy onslaught and were rewarded as Valdes redeemed himself deep into stoppage time following substitute Luca Toni's handball.