He has previously played in MLB for the Texas Rangers, San Diego Padres, and for the Hokkaido Nippon-Ham Fighters and Fukuoka SoftBank Hawks of Nippon Professional Baseball (NPB).

[5] He made his professional debut with the AZL Rangers, and also appeared for the Low-A Spokane Indians, posting a cumulative 2.75 ERA across 10 contests.

Martinez split the 2013 season between the High-A Myrtle Beach Pelicans and the Double-A Frisco RoughRiders, logging a 12–7 record and 2.50 ERA with 128 strikeouts in 1511⁄3 innings of work.

In his first career start against the Tampa Bay Rays, Martinez went six innings, struck out three and allowed three earned runs on four hits.

After two straight starts against the Oakland Athletics, the Rangers got Matt Harrison back from the DL and moved Martinez to the bullpen.

Upon reaching free agency and limited interest from MLB teams, Martinez signed a one-year, $1.8 million contract with the Hokkaido Nippon-Ham Fighters of Nippon Professional Baseball (NPB) on January 6, 2018.

[citation needed] On March 19, 2022, Martinez signed a major league contract with the San Diego Padres.

[18] On July 2, 2021, Martinez was named to the roster for the United States national baseball team for the 2020 Summer Olympics, contested in 2021 in Tokyo.