Diego Aguado Facio was born on 7 February 2007 in Madrid, Spain. He came through Real Madrid's La Fábrica and was promoted to Real Madrid Castilla in 2024, becoming a regular at the reserve level under Álvaro Arbeloa, who praised him as "a player perfectly aligned with the club's philosophy."
Aguado made his senior Real Madrid debut on 6 January 2025 in a 5–0 Copa del Rey win over Minera, marking him as one of the youngest 2007-born defenders to feature for the first team. In summer 2025 the club fielded — and turned down — a formal offer from Borussia Dortmund for the teenager, with Xabi Alonso explicitly blocking the move to keep him in the senior orbit. His current contract runs through June 2029.
A 1.86 m left-footed defender who plays primarily as a centre-back but can also operate at left-back, Aguado is known for his pace, passing range out of the back, and the kind of technical security La Fábrica defenders are expected to deliver. He is widely seen as a natural long-term successor to Antonio Rüdiger and David Alaba in Real Madrid's left-sided centre-back rotation.