SAN ANTONIO – Marc Castro scored a knockout Saturday night in his long-delayed pro debut.

The highly touted featherweight prospect dropped Luis Javier Valdes once apiece in the second and third rounds. Referee Mark Calo-oy stopped their scheduled four-round junior lightweight fight at 1:59 of the third round, as Valdes struggled to get up from the second knockdown.

The 21-year-old Castro, of Fresno, California, won his first professional fight immediately before the Canelo Alvarez-Callum Smith super middleweight title fight at Alamodome. Tijuana’s Valdes (7-6-1, 2 KOs) has lost three straight bouts, but the 21-year-old Mexican hadn’t been knocked out before Castro stopped him.

Castro finished Valdes with a right-left-right combination to the head, and then a left to the body as he went down to his gloves and knees. Castro first floored Valdes 1:15 into the second round, after hitting him with a right to the body.

Castro was supposed to make his pro debut August 15 in Tulsa, Oklahoma, but it was delayed because he tested positive for COVID-19 several days earlier. His debut was rescheduled for November 28 in Hollywood, Florida, but then Castro sustained an ankle injury while training.

That pushed back his long-awaited debut three more weeks.

Castro signed with Eddie Hearn’s Matchroom Boxing early this year. He initially was scheduled to make his pro debut April 17 in Oxon Hill, Maryland, but that card was scrapped due to the COVID-19 pandemic.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.