Valencia rates the United goalkeeper already among the best in the world.
He told Inside United: "He's been perfect in everything he's done. It's incredible what he's achieved. He's shown once again just what an important keeper he is for Manchester United. He's not far off breaking into the full Spanish national side. All his team mates here really hope that in two or three years he can be shot-stopping for Spain for the whole 90 minutes.
"He is proving here at United that he is one of the best goalkeepers around and I think that all of his team-mates are really happy and pleased to have David in such top form and we hope to be able to enjoy that for a long time to come."