|Full name||Diego Mainz García|
|Date of birth||29 December 1982|
|Place of birth||Madrid, Spain|
|Height||1.87 m (6 ft 2 in)|
|Playing position||Centre back|
|* Senior club appearances and goals counted for the domestic league only and correct as of 18 January 2016.
Born in Madrid, Mainz started his career at local Rayo Vallecano, going on to collect 36 appearances in La Liga (18 apiece from 2001 to 2003), his first being on 27 October as he played the full 90 minutes in a 2–1 home win against Deportivo de La Coruña. In the 2007 summer, as the capital club had slumped to the third division, he joined Albacete Balompié in the second level.
After two seasons as first-choice, Mainz was bought by Italy's Udinese Calcio, but was immediately transferred back to Spain with lowly Granada CF – eight other players made the same season-long move, after the two sides' partnership agreement. With the Andalusians he quickly established himself as an important player, helping to consecutive promotions in his first two seasons.
Mainz, who acted as club captain when available, scored his first goal in the top flight on 20 March 2012, but in a 3–5 away loss to FC Barcelona. He finished the campaign with 21 appearances in 1,780 minutes, to help his team retain its league status.
- El ímpetu del Rayo le basta para doblegar al Depor (Rayo's momentum is enough to down Depor); El Mundo, 27 October 2001 (in Spanish)
- Diego Mainz, nuevo jugador del Albacete (Diego Mainz, new Albacete player); Diario AS, 10 July 2007 (in Spanish)
- Diego Mainz e Iván Amaya jugarán en Segunda B con el Granada (Diego Mainz and Iván Amaya will play in Segunda B with Granada); Rayo Herald, 11 July 2009 (in Spanish)
- Diego Mainz y Dani Benítez, un año más en el Granada (Diego Mainz and Dani Benítez, another year in Granada); Marca, 20 June 2012 (in Spanish)
- Granada captain Diego Mainz looking forward to another Camp Nou test; Inside Spanish Football, 13 November 2013
- Barcelona 5–3 Granada: History-making Messi breaks club goalscoring record as gap at top of La Liga is reduced to five points; Goal.com, 20 March 2012