He previously vowed to win over head coach Zinedine Zidane, but the Spaniard is now on the verge of linking up with Milan for the 2020-21 season after flying into Malpensa airport on Wednesday.
Diaz declared himself "ready for this challenge" ahead of undergoing a medical and his representative Gonzalez is confident the ex-Man City product can become a key player at San Siro, having been underused by Zidane at Madrid.
"Brahim returned to Spain in January 2019, but in Madrid they didn't give him the required space and above all the confidence he needed," he told Tuttomercatoweb.
"He's a young player and he needs to play continuously to bring out his full potential.
"I'm convinced of the Rossoneri choice. Brahim has already lived abroad and will therefore adapt quickly to his new reality.
"His future team-mate Samu Castillejo, another great player I brought to Malaga, will help him. I say this with great pride.
"If Brahim Diaz has chosen Milan, it means he already knows he can help the team by carving out a leading role.
"I have no doubts about this. As soon as he has finished his growth path, we will talk about an absolute champion and not a promising youngster anymore."
Spain Under-21s international Diaz has scored two goals in 21 appearances for Madrid in all competitions during his 20 months at the club.