After starting his career in the lower divisions, he held several jobs at Sevilla, including as assistant and reserve team manager.

[2] Martínez retired from professional football at the age of 20,[3] and started his coaching career with Imperio de Albolote's youth categories, while also playing for their first team.

[10] After avoiding relegation with the reserve side, Martínez opted not to renew his contract, and was appointed in charge of Osasuna on 14 June 2017.

The youngest manager of the 2019–20 campaign, his side enjoyed their best-ever league start after achieving 20 points in ten matches, bringing the Nazaríes to the top of the tournament for two weeks.

[15] Martínez was awarded with the Miguel Muñoz Trophy (shared with José Bordalás) by Marca on 16 December 2019, for his efforts in the previous campaign.

[19] He then spent a season in England, watching football matches and learning from coaches including Pep Guardiola, Rafael Benítez, Frank Lampard and Xisco Muñoz.