Betis appointed Manuel Pellegrini as their new head coach on Thursday, and he knows Brahim well.
Brahim was in the Malaga youth ranks while Pellegrini was in charge, then the Chilean recommended Manchester City sign him.
In an interview with Real Madrid TV, 20-year-old Diaz said Pellegrini is a ‘special person’ for him and his family.
And that could lead the Spain under-21 international to Andalusia next season in search of minutes.
According to Mundo Deportivo, Brahim is an ‘express request’ of Pellegrini as he reshapes the Betis squad for next season.
Diaz has struggled for game time at Madrid since his €15.5m move from Man City in 2019.
He has not started a single La Liga or Champions League game for Los Blancos this season, making six substitute appearances.