*Club domestic league appearances and goals, correct as of 18:37, 29 January 2024 (UTC) ‡ National team caps and goals, correct as of 18:37, 29 January 2024 (UTC)
Martínez featured for Tigre in a youth tournament in Puerto Ordaz, where he played against the 2005 category of professional side Monagas, despite being a year younger.[2] These performances caught the eye of the Venezuelan Football Federation's technical director of development, Daniel Cesca, and contact was made with Tigre in 2017, with Martínez beginning to train with Monagas two times a week, while officially representing Tigre.[2] He went on to join Monagas permanently the following year.[2]
Having progressed through Monagas' academy, Martínez made his league debut in the 2022 season, coming on as a second-half substitute for Edgar Carrión in a 3–1 win against Mineros de Guayana. In only his fifth game for the club, he scored a long-range effort in a 2–0 win against Zulia.[3][4]
On 11 October 2023, he was named by English newspaper The Guardian as one of the best players born in 2006 worldwide.[5]
Martínez was called up to captain the Venezuela under-17 squad at the 2023 South American U-17 Championship.[8] He starred at the competition, scoring in Venezuela's first three games, before going on to score in a 2–0 win against Paraguay in the final phase to send Venezuela to the 2023 FIFA U-17 World Cup.[9] For his performances, he was lauded as Venezuela's star player at the tournament. Martinez has also played for the Venezuela under-23 football team.[10][11]
^Rodriguez, Jhosep (20 March 2023). "David Martínez liderará Vinotinto sub-17" [David Martínez will lead Vinotinto sub-17]. elorientaldemonagas.com (in Spanish). Retrieved 26 April 2023.