He has played in MLB for the Kansas City Royals,Texas Rangers and in Nippon Professional Baseball for the Yokohama BayStars.

He was subsequently dealt, along with starting pitcher Scott Kazmir, to the Tampa Bay Devil Rays at the 2004 non-waiver trading deadline.

Díaz received an opportunity when he was dealt to Kansas City in another deadline deal, this time on July 31, 2006, for outfielder-designated hitter Matt Stairs.

Weeks later, he received a call-up with the Royals and made his major league debut on September 6 against the New York Yankees at Kauffman Stadium in Kansas City.

He was called up to the majors on July 11, and made his Rangers debut the following day in a game against the Chicago White Sox.