Díaz returned to the team in 2017 after missing the 2016 season due to injury, and pitched to a 4.94 ERA with 40 strikeouts in 13 appearances.

In 2018, Díaz played for the rookie-level Greeneville Reds, posting a 3–3 record and 3.02 ERA with 67 strikeouts in 11 games (nine of them starts).

He split the 2019 season between the AZL Reds and the Single-A Dayton Dragons, logging a 7–4 record and 5.19 ERA with 77 strikeouts in 59.0 innings pitched across 27 appearances for the two teams.

[2] In 2021, Díaz played for the Double-A Chattanooga Lookouts, posting a 3.83 ERA with 70 strikeouts in 42.1 innings across 35 contests.

[4] He made his major league debut the following day against the Atlanta Braves, tossing a scoreless inning and collecting his first two strikeouts (Adam Duvall and Travis d'Arnaud).