Inter's "cursed" campaign looks set to continue until the final day after the 30-year-old fell awkwardly in a routine practice session.
The Italy international had only just returned to first-team action after a spell on the sidelines with a hamstring injury but he has now been ruled out of the Nerazzurri's final game of the season against Udinese.
"Antonio Cassano underwent medical tests that were made necessary following a fall during the final game during training today," a statement on the club's official website read.
"Tests showed a fracture of the second metacarpal of the right hand."
Inter has been forced to make do without a number of key players this season, with Diego Milito, Rodrigo Palacio and Javier Zanetti among several to have had their campaigns curtailed by injury.