Responding to criticism in the German press, Norbert Haug says Mercedes decided to oust Michael Schumacher after the seven time world champion’s "long period of reflection".
The German marque has poached Lewis Hamilton from McLaren, teaming him with Nico Rosberg for 2013 and beyond.
Former driver and German-language television pundit Christian Danner told DAPD news agency Schumacher was "dumped ice-cold", even though he has some sympathy for Mercedes on the basis that the highly rated Hamilton was on the market.
But German motor racing federation chief Hans-Joachim Stuck told Spox he was "shocked" when he heard Mercedes had dropped Schumacher.
"Hamilton is definitely one of the fastest formula one drivers, but for me he lacks the consistency.
"I don’t think Mercedes has done itself a favour," he added.
Another former German driver, Jochen Mass, told Auto Presse that the way Schumacher was dumped via press release was "below the belt".
But Mercedes’ Haug explained: "Michael has had a long period of reflection and was not definitively sure whether he wanted to go on or not."
When asked about reports the 43-year-old was only Mercedes’ ’plan C’ for 2013, Haug answered evasively: "Michael was informed that the team had to develop its alternatives, he was always informed and he accepted that," he is quoted by Welt.
Mercedes/Daimler chairman Dieter Zetsche is also on the defensive, insisting the Hamilton signing is "not a reproach" of the seven time world champion’s performance since 2010.
But he did admit to Bild newspaper that, "given the name of Michael Schumacher, expectations were probably too high" for his comeback.
"But I called Michael on the day the decision was announced to speak with him. It was a very good discussion," insisted Zetsche.
It is clear, however, that Schumacher’s next discussions are with teams that might want to take him on board for 2013.
Sauber, Williams, Lotus and even Ferrari have been mentioned, but the latter is almost certainly not in the frame.
Swiss commentator Marc Surer told Servus TV that Sauber is a "romantic" option given Schumacher’s pre-F1 sports car past, but thinks the financial aspect will spoil the deal.
"They would need a sponsor to pay Schumacher. So I believe that’s why this opportunity will fail," he said.
Danner, however, said Schumacher should push for Sauber if he still wants to have "fun" at grands prix.
But if Sauber is Schumacher’s only option, Gerhard Berger insists: "It’s time for him to stop.
"Schumacher is for Ferrari, Red Bull, McLaren or Mercedes. Everything else cannot be an alternative," the Austrian great told Auto Motor und Sport.
Berger does not scold Mercedes for moving on.
"You have to congratulate them," he said, "as with Hamilton and Rosberg they have a great driver pairing — probably the best.
"If you have the chance to get Hamilton, you really have to try," Berger insisted.
He also understands why Briton Hamilton needed a new challenge after six years with McLaren.
"Most drivers need a change of scenery after three or four years," said Berger, who in his career drove for teams including Benetton, McLaren and Ferrari.
"It brings you new motivation," he explained. "Of course the McLaren is the better car, but the appeal for him now is to make his Mercedes the best one."