Captain on the night, De Gea appeared to turn on his teammates after the loss this week.
"Even if I had managed to prevent the first goal, we would have conceded it later," stated De Gea in the aftermath.
In response, Galli told Il Corriere dello Sport: "A captain never says something like that," he stated. "In a situation like this, he should say the exact opposite.
"He comes into the locker room and says, 'Sorry, I could have done something more about the goal.' And then the spirit is different.
"And then... He conceded the first goal after ten minutes. Did he already understand that Fiorentina would lose? It means there's a lack of confidence. I have a lot of respect for De Gea, but this year he's unrecognisable."
Galli added, "This team should study communication. I never hear an interview where anyone talks about 'us.' Everyone thinks of their own little backyard."