His personal best jump is 18.18 metres, achieved in June 2024.[1] At the 2017 World Youth Championships he jumped 17.30 metres, a new championship record and world under-18 best mark, improving it further in 2018.
On 28 June 2021, he defected from the Cuban delegation sent to a preparatory competition in Castellón, Spain.[2] He thus missed the Tokyo Olympics.[3] He began to train under Iván Pedroso in Guadalajara.[2] Shortly after acquiring Spanish citizenship in 2022, Díaz beat the country's triple jump record.[4]
World Athletics declared Díaz eligible to represent Spain starting on 7 June 2024,[5] just in time to compete in the 2024 European Athletics Championships, where he won gold with a best jump of 18.18 m which put him third in the world all-time list.[6]