Sampdoria sank champions Inter Milan 1-0 with a second-half Giampaolo Pazzini goal to go top of Serie A on Saturday.
The forward sidefooted in a Daniele Mannini cross in the 72nd minute after a slip-up by Inter full back Davide Santon to give the Genoa side a home win and 15 points from six games.
Inter, who are two points behind in second spot, came close with a powerful Samuel Eto'o shot shortly before Pazzini struck, but the champions could have few complaints as they rarely had the Samp backline at full stretch.
Juventus, who also have 13 points, will go clear at the summit if they beat Bologna at home on Sunday.
Meanwhile, Fiorentina warmed up for the visit of Liverpool in the Champions League on Tuesday by beating Livorno 1-0 to draw level with Inter and Juve on 13 points.
Stevan Jovetic scored the only goal of the game from the penalty spot in the 76th minute as the Viola, who had Dario Dainelli sent off late on, made it two wins in four days.
The visitors had goalkeeper Sebastian Frey to thank for a string of marvellous saves to keep another crucial clean sheet.