Addressing the possibility of Schumacher joining the team, Vowles said: "I think we have to be straightforward about this: Mick is not special. He has just been good. I think he would come with a lot more experience than Franco does."
Schumacher is a Mercedes F1 reserve, with Wolff criticising his former strategy chief Vowles.
"I've obviously known James for many years, he's a strategist," Wolff explained to Sky Sports F1.
"Sometimes he says things too straightforwardly, that was a statement he could have done without.
"Mick has won everything there is to win, from F4, F3 and F2, and then of course operated in an environment with Gunther [Steiner], who is brutally tough and that was perhaps not what he needed to develop as a driver.
I think I'm with Toto here. Not choosing Schumacher is fine. Nobody is entitled to an F1 seat. And maybe Mick really is a worse choice. But to then say "Mick is not special" is just needlessly rubbing salt into the wound. He didn't need to insult one driver to defend his choice to go with another.
Some people love the 'brutal' part of being brutally honest a bit too much, I think.