Gonzales recently won a silver medal at a tournament in Paris and a bronze medal at the 19 and under amateur world championships in Cuba.
In 2002, he participated at a pro-am undercard headlined by professional world champion Acelino Freitas in Phoenix, Arizona, Gonzales' hometown. Such undercards are very rare in boxing, if not almost non-existent.
On June 12 of 2003, Gonzales surprised many of his fans by announcing he would turn professional soon after, under promoter Bob Arum. He cited amateur boxing politics as the reason why he decided not to wait for the 2004 Athens Olympic Games instead. In his professional debut, he defeated his opponent by first round knockout.
On October 4 of 2003, Gonzales scored one of the fastest knockouts in the history of boxing, needing only 16 seconds to defeat Josh Peters. Since this fight was shown as a part of the Erik Morales-Guty Espadas Jr Pay Per View offerings, it was Gonzales' first fight on Pay Per View. One week later, he had almost exactly the same result, when he beat an opponent 17 seconds into their fight in Arizona. Yet one more week later, he beat Roy Smith, also in Phoenix, by a knockout at two minutes and twenty five seconds of round one. He won once again, on Halloween night, with another first round knockout, his fifth consecutive first round knockout. On December 5, he was extended beyond the first round for the first time in his career, sustaining a bloody nose before rallying to knock out opponent Nate Martin in round four.
Gonzales was brought up being named "Ernie". He is 6-0 with 6 knockouts as a professional.