[4] He returned to continental level at the 2010 South American Youth Championships in Athletics and had his first success, taking the 1500 m gold on home turf in Santiago de Chile.

[8] He moved up another age category for the 2012 South American Under-23 Championships in Athletics and took the bronze medal, beaten this time by López, as well as Argentine Federico Bruno.

[9] He failed to improve his personal best in 2013, but took a silver medal behind Leandro de Oliveira at the South American Road Mile Championships and was runner-up at the inaugural Chilean National Sports Games.

[11] After a personal best of 3:40.24 minutes in July,[10] he scored two international bronze medals: first repeating his finish at the Ibero-American Championships, then coming third at the Pan American Sports Festival (Venezuela's Marvin Blanco won both times).

[13][14] At the age of twenty-one, Díaz established himself as one of the region's top middle-distance runners at the 2015 South American Championships in Athletics by securing his first senior gold in the 1500 m. – one of two winners for Chile at the meeting, alongside Víctor Aravena.