Inter Milan began their Serie A title defence with a 1-1 home draw with Udinese on Sunday after an Ivan Cordoba own goal in injury time, while AC Milan won 3-0 at promoted Genoa, helped by Kaka's brace.
Inter took an early lead through midfielder Dejan Stankovic after Zlatan Ibrahimovic's clever pass but goalkeeper Julio Cesar was sent off for handball outside the box on 57 minutes and the champions were unable to hold out.
Milan taught Genoa a lesson on their return to the top flight after a 12-year absence with Massimo Ambrosini's powerful header and Kaka's cool finish and penalty giving the European champions an easy victory.
Fiorentina had an equally comfortable 3-1 home win over Tuscan rivals Empoli to show they could still be a force this term despite striker Luca Toni leaving for Bayern Munich.
Adrian Mutu sliced through the defence to score the pick of the goals for Fiorentina, who like Milan were ruled out of last season's title race because of points deductions following Italy's match-fixing probe.
Juventus, demoted in the scandal, returned to Serie A with a thumping 5-1 home win over Livorno on Saturday.
Last season's runners-up AS Roma won 2-0 at Palermo in Sunday's entertaining late game with Philippe Mexes prodding home Rodrigo Taddei's cross early on and Alberto Aquilani scoring with a superb effort from distance.
PACKED AREA
Inter had looked well on the way to an opening-day
Cesar's dismissal put Inter on the defensive even more and they paid the price when defender Cordoba inadvertently flicked the ball into the corner as Udinese packed out the area.
Milan had no such trouble in Genoa despite away fans being controversially banned because of fears of revenge for the killing of a Genoa fan when the clubs met in 1995, the last time the west-coast club were in Serie A.
The promoted side offered little in attack and their defence allowed Ambrosini a free header on 21 minutes which set Milan on their way without having to step into top gear.
"Not everything was perfect but the team have had the right attitude," Milan coach Carlo Ancelotti told Sky Sport.
Napoli also found life tough back in the top flight and went down 2-0 at home to Cagliari.
Vincenzo Montella gave Sampdoria a 2-1 win at Siena with a fine late volley, having returned to his former club from AS Roma after eight years away.
The match of the day was in Parma where an entertaining 2-2 draw with Catania was overshadowed by visiting coach Silvio Baldini being sent to the stands in his first game in charge after kicking out at Parma boss Domenico Di Carlo on the touchline.