City risked losing Diaz for nothing as his contract at The Etihad Stadium was due to expire in the summer, before a deal with Real Madrid - which involves an initial fee of £15.5m - was struck.
Brahim joined City as a 14-year-old and was highly regarded by the club's academy staff. A woman told the paper that the unidentified...
"I understand the responsibility of playing with this shirt".
But, despite Guardiola's reluctance to let him go, it appears Diaz has decided that Real Madrid is where he will develop his career.
Qatar Open: Novak Djokovic beaten by Bautista Agut in Doha semi-final
With the quality of tennis displayed against Novak Djokovic , Roberto will be the favorite going into the finals. That's it, ' a frustrated Djokovic said in his post-match press conference.
"Today I close a chapter of my life and I say goodbye to Manchester City, the club where I have grown", Diaz posted in a statement on social media. I will give everything from the first day'.
Diaz, who will play under the number 21 jersey at Real Madrid, will join a talented group of young Spanish players at the club, which already includes Marco Asensio, Dani Ceballos, Marcos Llorente, Alvaro Odriozola and Sergio Reguilon.
The deal is part of Madrid president Florentino Perez's stated policy of snapping up the best emerging Spanish talent - with Brahim joining Marco Asensio, Jesus Vallejo, Dani Ceballos and Alvaro Odriozola in the Blancos squad.
He made just four appearances for City this season - three in the Carabao Cup and one in the Community Shield - with manager Pep Guardiola preferring to use more senior options in the Premier League and Champions League.
Manchester City have already suffered with the sale of youngster Jadon Sancho to Borussia Dortmund, where the Englishman has thrived, with other clubs keen to sign him up.