The Stadio Ennio Tardini outfit sit bottom of Serie A, but put in a creditable performance as they lost 1-0 to Juventus in the Coppa Italia quarter-finals on Wednesday.
That result comes against the backdrop of mounting off-field turmoil at Parma, with Cassano having left the club on Monday following a reported row over unpaid wages.
However, Donadoni has no plans to follow suit and suggested anyone who did would be making a selfish decision.
"It takes more dignity to stay in the saddle than to quit," he said. "It is easy for me to say I'll go because I don't get paid or because I have received other offers.
"It only makes sense to do your duty all the way.
"People mustn't think only of themselves, that is cowardly and hypocritical behaviour.
"If [on Wednesday] we fought on a par with Juventus, who are top of the table, then it means we can still challenge this season."
