Antonio has been dominating the sport of karate for some time in the kata division. His main rival was Luca Valdesi. Their meetings have been fierce, 19 in total, with the Venezuelan having won nine of their competitions. Díaz practices the style of Shito-ryu. He participated in his first Pan American Championship when he was thirteen years of age and won, for the first time, first place in kumite. Up to the age of seventeen he won mostly in the division of kumite.
Early years
Diaz's first achievement was reaching gold at the 5th Young Pan AmericanKarate Do Championship back in 1993 in Salinas, Puerto Rico. He participated in the young competitions until the 2000 staging held in Orlando, Florida, winning the event in the 18–20 years old category. He also reached the second place in the 1996 staging held in Margarita Island, Venezuela, and in 1998 in Buenos Aires, Argentina. He reached the third place in Medellin 1997. Diaz won his first Olympic Cycle competition at the 1998 Central American and Caribbean Games held in Maracaibo, Venezuela. Nowadays, Diaz holds the following medals in Olympic Cycle competitions: three gold medals at the Bolivarian Games, five at the South American Games, six at the Central American and Caribbean Games, and one gold and one silver at the Pan American Games. He participated at the Young WKF World Championship in 1999 in Sofia, Bulgaria, where finished ninth. Diaz has participated at the PKF Pan American Championship since 1998 achieving gold 16 times and reaching the podium in every edition. Diaz has two gold medals and three bronze ones achieved at the World Games. He finished at the third place at the 2017 edition. He won the two first staging of the Premier League Karate1 in 2011 and 2012.
The Karate World Championships are the highest level of competition for karate organised by the World Karate Federation. Antonio Diaz has reached the podium in the kata category eight times. He has won the gold twice, holding the world champion title. His first participation at the Karate World Championships was at the 13th edition held in Sun City, South Africa in 1996. He finished at the 17th place. Two years later, in Rio de Janeiro 1998, he reached the eighth place. He continued climbing positions as he reached the 5th place in Munich 2000. His earned his first medal in Madrid 2002 when he lost in the semi-finals against the Spanish Javier Hernández with the score 3–0. However, he won the bronze over the German B. Wolf. Monterrey 2004 was his second bronze medal after two repechage rounds. He won with a 5–0 score against the French Minh Dack and the Japanese H. Tsuchinda. Tampere 2006 became his third bronze medal. This time he would lose against the Italian Luca Valdesi in semi-finals. He won the repechage round against the English J. Motram with the score 4–1. Tokyo 2008 was his first time at the final round. He earned the silver medal after losing a tight battle against Luca Valdesi with the score 3–2. His first gold medal would come two years later in Belgrade 2010 against Valdesi with the score 4–1. In Paris 2012 he was World Champion again. Moreover, he finished with the perfect score of 5-0 all his encounters, an unprecedented situation in the competition. The final competition was against the local karateka Minh Dack. The 2014 championship held in Bremen, Germany, was not easy for Diaz. He encountered at first round Mattia Busato, who was the European champion at that time. Nevertheless, he won with the tight score 3–2. He fell in quarter finals against the German Ilja Smorguner. However, he won the bronze after two repechage encounters against Mehmet Yakan and Ibrahim Magdy Ahmed, with a 3–2 score in both of the times. He reached the podium in Linz 2016. This time he lost in semi-finals against Ryo Kiyuna with a 3–2 score, but he won the repechage with a 5–0 score against the Malaysian W. Lim Chee. In the 2018 World Championship held in Madrid, Diaz lost his semifinal found to Spain's Damian Quintero 0–5. He competed in for bronze against Ali Sofuoglu of Turkey. Sofuoglu competed with Gojushiho Sho and Diaz competed with Chatanyara Kushanku. Sofuoglu won 5–0.
Records
He won the 2012 World Karate Championships with a perfect score of 5–0 in every competition. Díaz is the only athlete that has been in the podium eight times in a row at the World Karate Championships. This record comprises his medals from 2002 to 2016. Thanks to this accomplishment, he was included in the Guinness World Records. He is the only American athlete that has reached 22 individual Pan-American medals. He won a medal in every competition. Additionally, between January 2010 and August 2012, he did not lose any international encounter. He kept the first place at the WKF ranking for 4 consecutive years.
Rivalries
Luca Valdesi
Between 2001 and 2012, Diaz encountered 19 times the Italian Luca Valdesi. Diaz won 9 times; their last encounter was during the Germany 2012 Premier League.
Akio Tamashiro
He encountered the Peruvian Akio Tamashiro 19 times. Diaz won 15 of those encounters.
Ryo Kiyuna
is the current world champion in the kata category. He has encountered Diaz 6 times; Diaz won five of these occasions.
