On August 25, 2008, Díaz was traded to the Pittsburgh Pirates as the player to be named later to complete a trade for José Bautista and was assigned to the Triple-A Indianapolis Indians.[2] After spending several days with Indianapolis, he was called up by the Pirates on September 2.[3] On September 7, 2008, Díaz got his first major league hit, a single off San Francisco Giants pitcher Jonathan Sánchez.[4]
Díaz began the 2009 season in Triple-A but was recalled to the Pirates late in April after starting catcher Ryan Doumit became sidelined with a broken wrist.[5] He would serve mainly as backup to fellow rookie catcher Jason Jaramillo and as an occasional pinch hitter. In his 31 games with Pittsburgh, Díaz compiled a .295 batting average and drove in 18 runs.[6] He was optioned back to Triple-A when Doumit returned from injury on July 10.[7]
On December 8, 2009, he was signed to a contract by the Detroit Tigers.[9]
Díaz spent the 2010 season as a member of the Toledo Mud Hens, finishing the season batting .255 with a home run and 21 RBI in 71 games.[10] He filed for free agency on November 6, 2010.
Texas Rangers
On January 18, 2011, he was signed to a minor league contract by the Texas Rangers.[11]
The Rangers re-signed Diaz to a minor league contract on August 12, 2012, and assigned him to the Triple-A Round Rock Express.[6] On November 3, he was declared a minor league free agent by Major League Baseball.[14]
Milwaukee Brewers
On January 18, 2013, Díaz signed a minor league contract with the Milwaukee Brewers.[15] He started the 2013 season with the Brewers' Double-A affiliate Huntsville Stars. He split the season with the Stars and Triple-A Nashville, where in 108 games total, he hit .302/.335/.433 with seven home runs and 42 RBI.[10] After joining the Sounds on June 29, 2013, Díaz closed out the year by hitting .328 (58-for-127) with four home runs and 20 RBI in 50 Pacific Coast League games.[10][16]
On October 1, 2013, Díaz signed a minor league deal with an invitation to spring training with the Brewers.[17] He returned to Nashville for the start of the 2014 season.[18]