De Gea's move to United is expected to be confirmed on Monday.
Osasuna keeper Ricardo said: "De Gea doesn't have nerves.
"I'm convinced that De Gea is good enough to play for Manchester United. He's big, quick and his concentration is at a high level throughout the game. He's comfortable with high balls and is very confident despite being so young.
"He does not worry when he plays against Barcelona or Real Madrid. That is a good sign because some goalkeepers become nervous when they play in front of big crowds in the biggest stadiums like Old Trafford. There are very few goalkeepers who can deal with that.
"Some goalkeepers need to feel the confidence of the manager. De Gea is the type of goalkeeper who can give the manager confidence."