Franck Kessie and Ricardo Rodriguez score for AC Milan in a match they controlled even though they could have been better in the final third.
Champions Juventus and AC Milan both recorded wins, but Napoli are top of Serie A.
AC Milan needed a penalty in each half to see off SPAL 2-0.
Mario Mandzukic fired Juventus to a 1-0 victory over fierce rivals Fiorentina in Turin.
Edin Dzeko scored twice as Roma piled on the misery for rock-bottom Benevento with a 4-0 victory.
There are few positives to take for Inter against Bologna, as Joao Mario and Antonio Candreva looked especially lost for Luciano Spalletti's side.
Cassano, 35, is without a club after leaving Verona less than a month after they had taken him on.
Inter Milan rejected Manchester United's offer for Ivan Perisic this summer because they are convinced they can be as successful as Manchester United.
Ahead of Juventus' match with Fiorentina, Federico Bernardeschi has seen little action thanks to his teammates' dazzling play in the final third.
Simone Verdi's stunning first-half strike grabbed a point for Bologna and wrecked Inter Milan's 100 percent start to the new Serie A season.
Kevin Strootman and Danilo Cataldi have a rivalry that extends to the Derby della Capitale. The pair will be reacquainted in Benevento on Wednesday.