(CNN) -- Giampaolo Pazzini scored the only goal as Sampdoria beat champions Inter Milan to leapfrog them at the top of Serie A on Saturday.
Pazzini scored a timely late goal for new leaders Sampdoria.
Samp lost 2-0 at Fiorentina in midweek, allowing Inter to assume the leadership, but showed their title credentials with a vital win on their own ground.
It was the first defeat of the season for Jose Mourinho's four-time defending champions.
Turin giants Juventus can go top if they beat Bologna in Sunday's matches.
Inter had generally the better of the first half, but strikers Diego Milito and Samuel Eto'o had few glimpses of goal as chances were a rarity.
Home goalkeeper Luca Castellazzi was called into action when Milito cut the ball back for Esteban Cambiasso to be denied by a fine save.
Inter made a brighter start to the second half, with Milito dragging a shot wide then slipping as he tried to convert a rebound in the penalty area.
Eto'o volleyed just wide before Pazzini put the home side ahead in the 72nd minute with a shot from close range after the Inter defense failed to cut out a Daniele Mannini cross from the right.
Mourinho's men pressed desperately for an equalizer and defender Lucio had the ball in the net only for it to be ruled out for offside.
Castellazzi then saved Lucio's firm free kick to secure three points for his side.
In Scotland, Celtic improved their position at the top with a 2-0 victory over St Mirren, while title rivals Rangers were held to a 0-0 draw by Aberdeen.
Paddy McCourt and Shaun Maloney scored for Celtic in an easy away win ahead of the Old Firm derby against champion Rangers next week.
In France, substitute Yannis Tafer and Bafetimbi Gomis scored second-half goals as Lyon came from behind to beat Toulouse 2-1 and top the table.
Lyon lead Bordeaux, who play Rennes on Sunday, by a single point.
Marseille's unbeaten run in the French league ended with a 3-2 loss at Valenciennes.