Affectionately known as "JIM" (his full name's initials), Martínez was appointed at Levante UD on 9 June 2011, replacing Getafe CF-bound Luis García.

[4] After two draws in the first two La Liga rounds he coached the team to seven consecutive wins, including a 1–0 home victory against Real Madrid.

[7] After ranking only 11th in the following season he opted to not renew his contract,[8] and signed a two-year deal with fellow league side Real Valladolid.

[10] On 11 December he was appointed at the helm of UD Almería, replacing fired Francisco;[11] on 5 April 2015, he was sacked by the Andalusians after a heavy 1–4 home loss to his previous club Levante.

[12] After one month as working as a personal assistant to Lorca FC's new Chinese owner Xu Genbao, Martínez moved abroad in November 2016 to manage Shanghai Shenxin F.C.

[15] Martínez was hired by Al-Arabi SC of the Kuwaiti Premier League in June 2019,[16] working alongside Darko Nestorović.