De Gea has struggled to reach the heights of last season, though Taibi insists his position with the Viola cannot be questioned.
Like De Gea, Taibi is also a former Manchester United goalkeeper, and told Radio Firenzeviola: "In Cremona, he made a key save on (Federico) Bonazzoli, and those are saves that ultimately win championships.
"De Gea has shown over the past two years that he's quite present in the most important matches, and last year he had an extraordinary season.
"The strength of the team also lies in when goalkeepers make key saves in these situations and help the team play better. De Gea cannot be questioned."
On Fiorentina's season, Taibi added: "I expected Fiorentina to be fighting for other positions in the table, whether they're late or early, the important thing is to get to the point. They're now four points ahead.
"They've recovered in a few weeks, but they've been more consistent than at the start. When things start badly, it's difficult to recover, so just staying up would be a great result."