Real re-signed Mariano following a year away in France after Lopetegui requested a No9 addition.
The coach reflected: "I spoke to him before his arrival. We are delighted with his return because he had a good season.
"He also knows the house and the requirements of Real Madrid, he knows what this shirt and this stadium represent. He will help us a lot. I called him to tell him what I thought of him from a football point of view.
"The season is long, there is room for everyone."