Raya has forced his way into Spain coach Luis Enrique's squad.
Frank told AS: "He is a top goalkeeper. Before being promoted to the Premier League I already knew him very well because I was with him for three years. He has a great character, he is a great professional, he is a hard worker, a very good guy.
"I only want good people in the dressing room and he is top. As a goalkeeper, there are several things that we take into account.
"First, he has to have good distribution with his feet. David has very good technique, he is very brave and he also keeps the line well, he is very good at anticipating. He is not the tallest, but he is enough.
"He is also good at one on one. I want the best for him and hopefully he will be the starting goalkeeper for the Spanish National Team. David has all the records to be one of the best."