Díaz signed with the Oakland Athletics as an international free agent on August 13, 2016.[1] As of 2021, in the minor leagues he had played 205 games at third base, 24 at first base, 12 at DH, 4 in left field, and one each at second base and catcher, and had a career slash line of .271/.324/.417.[2] On November 19, 2021, the Athletics added Díaz to their 40-man roster to protect him from the Rule 5 draft.[3]
2022
Díaz began the 2022 season with the Double–A Midland RockHounds, and was promoted to Triple–A after hitting .319 with 15 home runs and 58 RBI across 94 games. On September 17, 2022, Díaz was promoted to the major leagues for the first time.[4] He made his major league debut the following day against the Houston Astros, collecting his first career hit in the game, a single off of reliever Phil Maton.[5] In 2022 with the Athletics he batted .265/.294/.327 with no home runs and one RBI in 49 at bats, walking 3.9% of the time (as opposed to the league average of 8.3%).[6]
The Athletics optioned to the Triple-A Las Vegas Aviators to begin the 2023 season.[7] They promoted him to the major leagues on April 19.[8] On April 21, Díaz hit his first career home run, a go-ahead solo shot off of Texas Rangers reliever Will Smith at Globe Life Field.[9] On May 9, Díaz had his first multi-homer game, launching three home runs at Yankee Stadium against the New York Yankees. His first home run was a solo homer off of starter Clarke Schmidt, with his second home run also a solo homer off of reliever Albert Abreu, and his final blast a two-run homer off of Greg Weissert. In doing so, he became the only second baseman in franchise history to accomplish the feat alongside Héctor López.[10] In 90 games for Oakland, Díaz hit .221/.273/.364 with 10 home runs and 27 RBI.
2024
Díaz was optioned to Triple–A Las Vegas to begin the 2024 season.[11] In 29 games for Las Vegas, he hit .204/.288/.327 with two home runs and 10 RBI. On May 22, 2024, Díaz was designated for assignment by Oakland.[12] He cleared waivers and was sent outright to Las Vegas on May 27.[13] He elected free agency on November 6.[14]
Díaz has openly criticized the management of professional baseball in Colombia. In a 2023 social media post, he accused Edinson Rentería, a Colombian baseball executive and brother of Édgar Rentería, of stifling the growth of baseball in Colombia. "He is a person who deceives, abuses the trust, and defrauds... I hope that people realize this, that is why I make this message public."[18] Rentería responded by saying he would take legal action against Díaz.[19]