The club have completed the permanent signing of 16-year-old Greek defender Spyridon Petros Zormpas from Olympiacos, the most decorated club in Greek football, where the 2010-born centre-back had been progressing through the youth ranks.
Standing at 190cm, Zormpas is a physically imposing prospect, and the transfer contract has been formally deposited with the Serie A league registry to complete the move.
At the other end of the squad, AC Milan have also reached an agreement to keep hold of Modrić for a further season, with the Croatian set to sign a new contract running until 2027. Head coach Rúben Amorim made his admiration for the veteran midfielder clear during his unveiling press conference, describing him as hugely important to the club's plans.
"He's a player we want to keep, I've spoken to him twice," Amorim said. "If needed I can go and speak to him again, I never get tired of it.
"He's incredible, he's a reference point for us. I won't tell you he'll play every match, but we want to count on Modrić for next season."
The signature on the new deal is expected in the coming days, after which Modrić will link up with his team-mates for Milan's pre-season tour of Australia. The 40-year-old has been one of the most influential figures in Milan's squad since arriving, and his willingness to extend his stay will come as a significant boost to Amorim as he continues shaping his first campaign in charge.
Taken together, the two pieces of business reflect Milan's approach to squad building this summer: investing in academy talent capable of developing over the coming years, while also ensuring experienced, high-quality figures remain in place to guide a squad that will feature a number of younger faces once the transfer window closes.
Zormpas has already represented Greece at youth international level, featuring for both the country's Under-15 and Under-16 sides, and is expected to join Milan's youth setup as he continues his development in Italian football.
His arrival adds further depth to a defensive pipeline the club has been keen to strengthen, while Modrić's extension ensures a wealth of experience remains available to the squad's younger contingent as they adjust to life under a new head coach this season.