Díaz began playing in Puerto Rico at local club Caguas Bairoa.
[2] Gerald was called up in 2016, for the Puerto Rico under-20 national team, for the first round of World Cup qualifiers.
[3] He made his debut with the senior Puerto Rico national team in July 2017, in a friendly match against Indonesia.
[5] In July 2019, he played for the Puerto Rico national under-23 football team for the 2020 Olympic Games qualification where he scored one goal.
On June 18, 2023 he scored the winning penalty in a shoot-out against Suriname in the 2023 CONCACAF Gold Cup qualification match, taking Puerto Rico to their highest achievement in the competition's history to date.