López was an all-district football player at Corpus Christi Moody High School and went on to play linebacker at Sam Houston State University before ever boxing in the amateur ranks.
López was a two-time Texas Golden Gloves Champion and won a silver medal at the 2005 U.S. National Championships in the Light Heavyweight division.
[1] With a short-lived amateur career, López decided to turn pro in 2007 after his graduation from Sam Houston State University.
In April 2010, in Corpus Christi, Texas, Alfonso won a six-round unanimous decision victory over Gabriel Holguin.
[2] On November 4, 2010, Lopez fought for the vacant WBC Continental Americas Super Middleweight Championship in Dallas, Texas.
After almost 2 years off due to another injury, El Tigre returned to the ring March 24, 2017 against Colby Courter at the Humble Civic Center.
After sustaining a cut over his right eye, Lopez stopped Colombian Milton Núñez in the final round of their bout to retain the American Boxing Organization Light Heavyweight Championship.
Theran refused to come out for the fifth round and the TKO victory made López the new WBO NABO Light Heavyweight Champion.