Lucien Favre has been disrespectful to Borussia Monchengladbach by announcing his resignation on Sunday night, according to Felix Magath.
The Swiss coach released a statement saying that he had tendered his resignation since he no longer felt he was the "perfect coach" for the club, after losing the first five games of the season.
His announcement came after a day of talks with club bosses, who had tried to convince him to stay on.
Gladbach, who have called a press conference for Monday afternoon, have rejected Favre's resignation and former Bayern Munich and Fulham coach Felix Magath says they are right to be disappointed with his actions.
"In my eyes, the way he has left wasn't clean," Magath told the Tz newspaper. "Announcing his resignation without consultation with the club was wrong.
"By doing that, Favre has snubbed the club who wanted to get through this crisis with him and put them into a difficult situation."
There was praise from another former Bayern coach, on the other hand, with Ottmar Hitzfeld telling Switzerland's Blick newspaper that he "warrants my respect."
"Only Lucien Favre can really judge the situation and draw his conclusions," added Hitzfeld.