Ronaldinho scored twice after Alessandro Nesta gave AC Milan the lead in a 3-0 win over Juventus on Sunday that put their side in control of second place in Serie A.
Nesta scored in the 29th minute after being left unmarked at the far post for a corner, while Ronaldinho headed in from another corner in the 72nd before finding the target from close range in the 88th.
Milan now has 37 points, eight behind leader Inter Milan, while third-place Juve is level on 33 points with Napoli.
Inter needed an injury-time winner from Walter Samuel to beat last-place Siena 4-3 on Saturday.
In his second game since rejoining Milan on loan, David Beckham again lined up on the right of a three-man attack and had a solid if not spectacular match.
Nesta scored after Juve's Christian Poulsen and Felipe Melo both failed to clear the ball, while Ronaldinho's first goal deflected in off Juve defender Paolo De Ceglie. Both the corners for Milan's opening goals were taken by Andrea Pirlo.
Earlier, Napoli extended its unbeaten run under new coach Walter Mazzari to 12 matches with a 1-0 victory over Sampdoria.
Argentine striker German Denis scored with a header in the 71st minute for the southern club.
Change is good
After gaining only seven points in its opening seven games, Napoli replaced Roberto Donadoni with Mazzari and hasn't lost since.
"You have to approach the games the way we've been approaching them," Mazzari said. "All games are difficult. The details make the difference and we're working on the details, plus we're a young team."
Denis came on during the first half after fellow Argentine Ezequiel Lavezzi limped off with a muscle strain that could result in a month on the sidelines.
"It's important that everyone remains ready for when they have to play," Mazzari added.
AS Roma, which beat Chievo Verona 1-0 Saturday, is fifth, followed by Fiorentina and Palermo, who both won Sunday and have 30 points each.
Fiorentina rallied to beat Bari 2-1 in a match that both sides ended with 10 men, while Palermo edged Atalanta 1-0 with a 70th-minute penalty from Edison Cavani.
Bari's Brazilian forward Paulo Barreto and Fiorentina's Romania international Adrian Mutu both scored from headers in the first half.
Bari was reduced to 10 men when Sergio Almiron picked up his second yellow card in the 58th minute.
Castillo nets winner
Argentine striker Jose Castillo scored the winner in the 74th, knocking in the rebound off a shot from Riccardo Montolivo that hit the crossbar, his first goal since joining Fiorentina.
Castillo then received a straight red card in the 80th for tackling Bari's Pedro Kamata from behind.
Elsewhere, Francesco Tavano and Cristiano Lucarelli scored in Livorno's 2-1 victory over Parma and Alessandro Matri had a tap-in goal for Cagliari in a 1-0 win over Bologna.
Genoa beat 10-man Catania 2-0 with goals from Giandomenico Mesto and Giuseppe Sculli, with Catania manager Sinisa Mihajlovic getting sent off for protests near the end.
Antonio Di Natale scored his league-leading 12th goal for Udinese in a 1-1 draw with Lazio, which had taken the lead with another goal from newly signed Sergio Floccari, his third in two games.