Ronaldinho scored his first goal in Italian football to give AC Milan a vital 1-0 victory over Inter Milan in a pulsating city derby at the San Siro.
Inter Milan had two players sent off -- although Marco Materazzi was dismissed after he'd been substituted -- as Jose Mourinho tasted defeat as Inter coach for the first time.
It means that despite losing their first two matches, Milan are right back up in the thick of the title race having won their next three in a row.
Ronaldinho dedicated his goal to the Milan fans and club president -- and Italy prime minister -- Silvio Berlusconi, who celebrates his 72nd birthday yesterday.
"I'm very happy, I was hoping to score a goal. This one is for the fans who've made me feel at home," said the Brazilian.
"It's a moment of great happiness, I know tomorrow is president Berlusconi's birthday, this goal is for him."
Previous leaders Inter drop down to fourth with the loss as the Serie A table takes on an unfamiliar look.
Lazio are the new Serie A leaders after they won 3-1 at Torino while Napoli, one of only two remaining unbeaten teams, are up to an unlikely second following their 1-0 success at Bologna.
Udinese are third having won 2-1 at home to Siena while Catania, who beat Chievo 1-0, are fifth ahead of Milan and Juventus.
In Milan Inter had more of the ball but Milan were looking dangerous on the break and on 25 minutes Kaka beat Maicon down the left before crossing for Ronaldinho, whose left foot shot was blocked by goalkeeper Julio Cesar.