He played in Major League Baseball (MLB) for the Toronto Blue Jays and the Boston Red Sox.

Diaz went to Coral Gables Senior High School, where he was teammates with Yonder Alonso and Eddy Rodríguez.

Diaz, who played summer collegiate ball in 2005 with the Thunder Bay Border Cats, was selected in the 12th round (360th overall) by the Toronto Blue Jays in the 2006 MLB Draft.

Diaz started 2008 with High-A Dunedin, but he was promoted to Double-A New Hampshire on May 18, where he went down and up 4 more times before finishing with the Fisher Cats.

He was demoted back to New Hampshire on June 21, where he stayed before earning a one-week promotion to Las Vegas at the end of the season.

Diaz went to spring training with the Blue Jays in 2011, and was one of the final cuts, staying as insurance for Aaron Hill, who was returning from a quadriceps injury.

Diaz was the Fisher Cats Opening Day second baseman in 2011, where he played before being promoted to Las Vegas on April 23.

On May 15, he was placed on the disabled list with an injury, and after rehabbing in Dunedin, he returned on July 5 with New Hampshire, where he played the rest of the season with.

[4] He hit .240 in 22 games with the Red Sox in spring training before being cut on March 25 and assigned to Triple-A Pawtucket.

Diaz was familiar with the Red Sox defensive system because of his experience with John Farrell, Brian Butterfield, and Torey Lovullo during his time in the Toronto organization.

Diaz returned to the Blue Jays on November 11, 2013, on a minor league contract with an invitation to spring training.

[25] He was assigned to the Triple-A Buffalo Bisons to begin the year, and also spent time with the Double-A New Hampshire Fisher Cats.