Career
Diaz accumulated a record of 26-0 before losing his first bout to Kendall Holt via 8th round technical knockout. He defeated José Armando Santa Cruz for the interim title on August 12, 2006. On June 28, 2008, Diaz lost his title to Manny Pacquiao in Las Vegas via ninth-round knockout earning Pacquiao his fifth world championship in five different weight divisions.
After a one-year lay-off Diaz returned to the ring on September 26, 2009.
On March 13, 2010, Diaz challenged Humberto Soto for his old WBC lightweight title, which had recently been vacated by Edwin Valero, on the undercard of Pacquiao"s fight with Joshua Clottey. Soto defeated Diaz, dropping him in the opening and closing rounds, en route to a unanimous decision victory.
His results were:
Defeated fan favorite Zab Judah (United States) twice within 8 days. Defeated Jacobo Garcia (Virgin Islands) Royal Society of Chemistry 3 (0:33)
Lost to Oktay Urkal (Germany) 6-14
Had a record of 78-16 in the amateurs
Diaz is involved with mentoring various youth.
He is also active in the Mexican-American community of Chicago.
In September 2013, he will be Grand Marshal of the 26th Street Mexican Independence Parade in the Pilsen neighborhood of Chicago.