A two-goal blitz from striker Diego Milito gave Serie A champions Inter Milan an unconvincing 2-1 win at Cagliari on Sunday, while AC Milan also struggled to beat Bologna 1-0.
Inter fell behind on Jeda's first-half penalty after Maicon had been adjudged to push over Alessandro Matri in the box.
Coach Jose Mourinho, who was later sent to the stands for arguing with officials, brought on forward Mario Balotelli at the break to change shape, and the move paid dividends just as it had in the previous weekend's 2-0 win over Parma.
Good pressure by Samuel Eto'o forced the home defence to give the ball away and Argentina's Milito ran through to score on 51 minutes before dinking in a second goal five minutes later following a long ball over the top.
Milito, who signed for Inter in the transfer window following a successful spell last season at Genoa, took his tally to an impressive 28 goals in 35 Serie A appearances.
Inter, who drew 0-0 with holders Barcelona in the Champions League on Wednesday, are third in the table on 10 points.
Leaders Juventus made it four wins from four in Saturday's 2-0 victory over Livorno and Sampdoria joined them at the top after securing maximum points from the first four games of the season for the first time, finishing with a 4-1 thrashing of Siena.
Clarence Seedorf, playing in place of flu victim Ronaldinho, netted a classy goal in the second half to hand Milan victory, but visitors Bologna had chances to snatch a draw at the end.
Seedorf won the ball on the edge of his own box and, despite Bologna appeals for a foul, he laid the ball off to Massimo Ambrosini and charged up field.
Ambrosini found the Dutchman with an intelligent pass and Seedorf cut through a weak defence to score from close range.
Substitute Filippo Inzaghi, who replaced the ineffective Klaas Jan Huntelaar, hit the post late on but the Rossoneri remain a work in progress after an inconsistent start to the season.
Genoa, who like city rivals Samp were going for a fourth straight win, lost its 100 percent record in a 3-1 defeat at Chievo.
Julio Cruz grabbed a 1-1 draw for Lazio at Catania while promoted Parma beat coach Francesco Guidolin's former side Palermo 1-0, and Atalanta stayed bottom with no points after a 4-1 loss at Bari. AS Roma host Fiorentina later (1845 GMT).