Diaz was born in New York and raised in Katy, Texas. He attended Katy High School, where he received All-district and All-conference honors at offensive tackle as a senior.
In 1997, he became a regular starter at right guard in the first 13 games, moving to left guard for the last 3 contests. He was a part of a rushing attack that included running backsMike Alstott and Warrick Dunn. In 1998, he started the first 12 games at left guard, before missing the rest of the season with a broken left foot.
In 1999, he started the first 11 games at left guard, before being passed on the depth chart by his former college teammate, Kevin Dogins. He returned to the starting lineup for the season finale against the Chicago Bears and the playoffs. He was waived on March 17, 2000.[5]
Dallas Cowboys
On March 31, 2000, he signed as a free agent with the Dallas Cowboys, appearing in 9 games as a reserve player. He was released on March 1, 2001.[6]