Real are set to trigger the buy-back clause in Mariano's OL deal - just 12 months after selling him to the French giants.
AS says Lopetegui called Mariano earlier this week to sound him out about a return to Madrid and whether he was prepared to make the move. After the conversation, the coach was satisfied with what he heard and approved the deal.
Lopetegui made it clear to Mariano that he would not be a first-choice, but the striker was willing to accept the role.
Mariano, 25, was born in Barcelona and trained in the junior teams of Badalona until he was signed for Madrid's youth in 2012. He then went through Madrid C and Castilla before reaching the first team in 2016.