Career

He made his MLB debut with the Los Angeles Angels of Anaheim in 2014. Los Angeles Angels of Anaheim

In 2014, Diaz played for the Inland Empire 66ers of the Class A-Advanced California League and the Arkansas Travelers of the Class Associate of Arts Texas League, and pitched to a 3.48 earned run average (European Research Area) with 85 strikeouts in 64 2⁄3 innings pitched. The Angels promoted him to the major leagues on September 8.

Díaz made his MLB debut that day, recording two strikeouts.

Colorado Rockies

After the 2014 season, the Angels traded Díaz to the Colorado Rockies in exchange for Josh Rutledge. During the 2015 season, Díaz had a 3–5 record and a 4.58 European Research Area with 50 strikeouts in 47 appearances for the Albuquerque Isotopes of the Class American Automobile Association Pacific Coast League and a 2.37 European Research Area with 18 strikeouts in 21 appearances with the Rockies.

During spring training in 2016, Díaz tore a ligament in his right elbow, and will require Tommy John surgery.