The news of his passing was shared by WBC president Mauricio Sulaiman, who took to X.

“It is with deep sadness that I have learned of the passing of my dear friend and champion Ruben Castillo,” Sulaiman said. “Now he is in the arms of God. May his wife Cindy, family and friends find comfort with the support of the so many who loved Ruben. Rest in eternal peace.”

Castillo was born in Billings, Montana, the second youngest of five children, on December 19, 1957. His family moved to Lubbock, Texas before settling in Bakersfield, California.

Boxing wasn’t Castillo’s first love, that was baseball. His father played for the Texas Rangers farm club and his older cousin, Babo Castillo, played Major League Baseball for the Los Angeles Dodgers and Minnesota Twins.

He once told The Ring that he pursued boxing because he was too small for baseball. Castillo went on to be a good amateur, going 49-1, before turning professional at just 17 in February 1975.

Castillo was active and impressively took his record to 44-0 (21 KOs), beating the respected trio of Hector Carrasquilla (TKO 3), Fel Clemente (UD 10) and Juan Escobar (TKO 8) in 1979. Those wins set the table for a world title challenge in early 1980.

He came up short against WBC junior lightweight champion Alexis Arguello (TKO 11) in January 1980, three-months later, he was bested by WBC featherweight ruler Salvador Sanchez (UD 15). Castillo lost a third title tilt, this time to WBC featherweight titlist Juan Laporte (UD 12) in February 1983.

He thought about walking away, but Castillo ultimately stuck around while hoping for his next big opportunity.

“Don calls me up and says, ‘There’s a kid who just won the [WBC 130-pound] title against [Mario] ‘Azabache’ Martinez,’ ” Castillo said during an interview in 2021. “He’s a brand-new kid. You’ll beat his arse, you’ll become the champion and we’ll sign a big contract.’ You know who that guy was? Julio Cesar Chavez.”

Chavez stopped Castillo in the sixth round for the WBC junior lightweight title in April 1985. Castillo fought a few more times before embarking on a comeback in the mid-1990s. His record was 68-10-2 (35 KOs).

In retirement, Castillo worked as a broadcaster alongside the legendary Chick Hearn.

“Timing is everything and, in my era, it just was not the time,” Castillo said, reflecting on his career. “If I was fighting now, I’d have five belts.”