Hopkins (right) made his pro debut before 27-year-old Joe Smith Jr was born.
Bernard Hopkins suffered defeat in his final fight after the 51-year-old was knocked out of the ring in the eighth round by Joe Smith Jr.
A flurry of punches sent Hopkins through the ropes and, after he failed to return to the ring in 20 seconds, he was beaten by technical knockout.
Hopkins said he was “shoved” and hit his head in his fall in the light heavyweight bout.
He added he twisted his ankle and “couldn’t stand up”.
Hopkins confirmed the fight would be the last of his 28-year career, which he ended with a record of 55 wins (32 KOs), eight defeats, and two draws.
The former two-weight world champion defended his world middleweight title 20 times between 1995 and 2005 and is the oldest man to hold a world title, aged 49.
The American had never been beaten inside the distance before his defeat by compatriot Smith Jr in his first fight since losing on points to Russia’s Sergey Kovalev two years ago.
Smith was ahead on points on two of the judges’ scorecards before he ended the fight with a series of punches which culminated in a left hook that sent Hopkins through the ropes in Los Angeles.
“I’ve seen him fall and I kept hitting him,” Smith, 27, said. “I landed that left hook at the end there to finish the job.
“I hit him with four or five clean shots there, good shots right on the button.
“I didn’t expect him to get up but he is a true champion. I came here to do my job. This is my coming out party. I had to finish him.”
Meanwhile, Ukraine’s Oleksandr Usyk, the 2012 Olympic heavyweight gold medallist, defended his WBO cruiserweight title with a knockout of South African Thabiso Mchunu in the ninth round.
Source: BBC Sports