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."
'People will remember us because we got to No.1 in the world rankings and achieved great things - but our biggest regret is that we didn’t win anything': Ex-Everton star Kevin Mirallas opens up on 'honour' of being part of nation's golden generation
‘I’m sure we’d have finished in the top four or five if he hadn’t joined Chelsea in January. Him leaving damaged the team, but we couldn’t stand in his way’: Alan Curbishley reflects on failed Champions League dream after selling key player
