AC Milan, hit by a flurry of close-season departures, fully justified their fans' trepidation over the new season by losing 1-0 at home to promoted Sampdoria in their opening Serie A match.
Andrea Costa headed the only goal for the visitors just before the hour to stun a half-empty San Siro on a hot, summer's evening, making it painfully obvious that the 18-time Italian champions are in for a long, difficult season.
Inter Milan and Napoli had no such problems, starting with 3-0 wins at Pescara and Palermo respectively.
Dutchman Wesley Sneijder and Argentine forward Diego Milito scored twice in two minutes early on for Inter before Brazilian Philippe Coutinho added the third in the 81st minute on an unhappy Serie A return for Pescara after a 19-year absence.
Antonio Cassano, who joined Inter from neighbours Milan in a swap with Giampaolo Pazzini, set up the second goal.
Marek Hamsik put Napoli ahead in first-half stoppage time and Christian Maggio and Edinson Cavani added two late goals as they made light of Ezequiel Lavezzi's absence after the Argentine forward was sold to Paris Saint-Germain.
Eighteen-year-old Uruguayan Nicolas Lopez scored a stoppage-time equaliser five minutes after coming on as a substitute to give AS Roma a 2-2 draw at home to Catania. Brazilian midfielder Hernanes gave Roma's neighbours Lazio a 1-0 win at Atalanta.