The £18m signing from Barcelona has enjoyed a impressive first season at Goodison.
"He is one of the best, I don't have doubts about that. He is proving that," Silva said.
"I do not have all the names in my mind at the moment but Lucas has stayed there with the best.
"If he is the best one....always I will push for my players but Lucas is there in the top list of the best left-backs."
"Robertson is a very good one also. He is a fantastic boy, a fantastic professional," Silva said.
"He is our rival but he deserves everything he is achieving in his career but Lucas is Lucas, and Lucas, for me, is the best one because he is our player and playing in our blue shirt.
"We are really happy with him, he is enjoying his football and our fans love him and he has been everything we expected when we signed a player such as him."
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