Brazil playmaker Kaka scored his first goal, a delightful curling shot, since his return to AC Milan at the start of the season but his struggling team were held 1-1 at home by Lazio in Serie A on Wednesday.
Second-placed Napoli won 2-1 at Fiorentina who were furious after midfielder Juan Cuadrado was sent off after twice being booked for diving in the penalty area, with the second incident coming in stoppage time.
Champions Juventus, helped by a trademark Andrea Pirlo free kick, trounced Catania 4-0 to stay level on points with Napoli.
Napoli and Juventus have 25 points from 10 games, two behind leaders AS Roma who host Chievo Verona on Thursday.
Kaka, back at the San Siro after four unhappy seasons with Real Madrid and recovered from a thigh injury he suffered in his first game, gave Milan the lead in the 54th minute.
Lazio replied with a goal from defender Michael Ciani, leaving Milan 10th on 12 points.
"I am always working hard," the Brazilian told the ANSA news agency. "I don't know if I can go back to play at the level of eight years ago but I'm trying very hard.
"Everyone is saying I am giving a lot to Milan. I want to play in the World Cup in my country next year and this is where Milan is helping me."
Jose Callejon gave Napoli a 12th minute lead at Fiorentina when he volleyed in Gonzalo Higuain's cross but the hosts levelled with a penalty converted by Giuseppe Rossi, his ninth league goal of the season.
The spot kick was awarded after Matias Fernandez went flying, a harsh decision hotly protested by the Napoli players.
Cuadrado hit the post for Fiorentina before Belgian Dries Mertens put the visitors back ahead in the 36th minute.
Fiorentina left the field fuming after they had three penalty appeals turned down after the break, two from Cuadrado and one by Rossi. The referee showed a yellow card for simulation each time.
Gokhan Inler appeared to make contact with Cuadrado in the last of the three incidents although the Colombian exaggerated when he went down.
Arturo Vidal put Juventus ahead with a deflected shot before Pirlo struck with a typically brilliant free kick before halftime.
Carlos Tevez and Leonardo Bonucci added two more goals in the second half.
Alberto Gilardino made up for a second-minute penalty miss by scoring the winner as Genoa overcame Parma 1-0 and Livorno recovered from conceding two goals in the first eight minutes to draw 3-3 at home to Torino.