Martinez joining Manchester United in deal reportedly worth initial €55M
The transfer is subject to a "medical, to player terms being finalized, and to UK visa requirements," United's statement read.
The 24-year-old, who was named Ajax's Player of the Year for the 2021-22 season, will ink a five-year contract to join the Red Devils, according to The Guardian's Fabrizio Romano. There is an option for another season to be added to his paperwork.
The Dutch club will apparently receive €55 million up front with the potential to earn further performance-related payments.
Martinez regularly operates to the left of a central defensive partnership but has stepped up into midfield in the past. New United boss Erik ten Hag signed him for Ajax from Defensa y Justicia in 2019.
Ten Hag appeared to be preparing for Martinez's arrival when he moved Harry Maguire from his usual position as the left-sided center-back to a role on the right of the central pairing during Friday's victory over Melbourne Victory, BBC Sport's Simon Stone reported.
The other senior center-backs currently on United's books are Raphael Varane, Victor Lindelof, Eric Bailly, Phil Jones, and Axel Tuanzebe. Youngsters Teden Mengi and Di'Shon Bernard could leave the club on loan, according to Richard Fay of the Manchester Evening News.
So far this summer, Ten Hag has overseen the signings of left-back Tyrell Malacia and playmaker Christian Eriksen. United's apparent lack of ambition in the transfer market reportedly led Cristiano Ronaldo to request a move from the club.
United are understood to have an €85-million agreement in place with Barcelona for the signing of Frenkie de Jong, but the midfielder is reluctant to leave Camp Nou. The Dutchman traveled for Barca's preseason tour of the United States.