Carlos Ocampo, at only 22 years old and a 100-1 underdog, was knocked out in bad fashion in the biggest fight of his career.

And that biggest fight only lasted a single round.

The International Boxing Federation made him the mandatory challenger a few months, and Ocampo challenged their welterweight champion, Errol Spence, on Saturday night in Texas.

Spence retained his IBF welterweight title with very few issues, but he said he was disappointed for the fans.

Spence, nicknamed 'The Truth', improved his record to 24-0 with a 21st knockout of his career late in round one, Ocampo taking a wicked hook to the body before being counted out.

And he stayed down for quite some time when the referee finished his full count.

Ocampo had no excuses in the first loss of his career and admits that he didn't show Spence enough respect in the ring and got reckless. 

"I got overconfident at the end of the round and he caught me," said Ocampo, who fell to 22-1 with 13 knockouts.

It's still a mystery on who Ocampo earned his position - when the boxer never fought outside of Mexico or beat anyone of note to secure that position.

A crowd of over 12,000 was in attendance, but Spence was hopeful of a better work out.

"I was a little disappointed," Spence admitted. "I wanted to give the crowd their money's worth. I wanted him to sustain a bit and give him some punishment, but the body shot got him and I dropped him.

"It was a great victory. It was really short, so it was hard to describe. I took my time, tried to use my jab. I thought he was going to be a little bit tougher but I hit him with a body shot. I don't get paid for overtime. If I can get him out first, great, but I wanted to carry it, go to the fourth or fifth round for the fans."