"I thought I'd try out some new players because this is one of the last opportunities," Donadoni said.
"Cassano is a player who I know best," the former Livorno tactician continued. "He needs to be stimulated and call-ups don't do that. He needs to grow more, so I am waiting expectantly."
Del Piero's chances of making Euro 2008 his Azzurri swansong are up in the air after the Juventus talisman was again left out of the squad.
"Scoring seven goals is not enough to make a player indispensable," Donadoni maintained.
"Del Piero knows very well what the situation is. Four months ahead of the European Championships nobody should feel excluded.
"If I made my list definite for Austria then the players that were on it would go on holiday, instead I will follow all the games and collect information."