By Rick Reeno

Mandalay Bay, Las Vegas - On Saturday night, a fighter trained by Abel Sanchez will attempt to add the first blemish to the undefeated record of WBO/WBA/IBF light heavyweight champion Sergey Kovalev.

Sanchez's fighter, Nadjib Mohammedi, will enter the ring as a significant underdog against one of the most feared boxers in the sport. HBO will televise the fight live.

Sanchez is very familiar with Kovalev, as he trained the hard-punching Russian early in his career. Kovalev's trainer for the last few years has been John David Jackson.

The star fighter of Sanchez's stable is WBA/IBO middleweight champion Gennady 'GGG' Golovkin.

Over the years some rumors have circulated regarding the details of some sparring sessions between Golovkin and Kovalev at Sanchez's gym in Big Bear, California.

As the story goes, Golovkin practically manhandled Kovalev during their gym battles.

According to Sanchez, most of the stories regarding those sessions are missing important details - like the gap in experience between the two fighters.

"When Kovalev first came to me he had nine fights. He was a young man, not in age but in boxing ability. When he came to me, Golovkin was already a world champion and a silver medalist in the Olympics, over 300 amateur fighters….he had all these credentials. So when they sparred, it was a like a very experienced guy against a very inexperienced guy – so of course Golovkin got the best of him," Sanchez explained to BoxingScene.com.

"I had him for eight fights and by the tail-end, he had improved dramatically. And I think since he left my gym, which I think was after 19 fights, John David has done a magnificent job with him and he’s evolved into a killer. That guy that we see on Saturday night is not the guy who left my gym, because the guy who left my gym was still a pup."

"So as far as him and Golovkin sparring, yes [Golovkin got the best of him], but it wasn’t just Kovalev [who got bested] – it was everyone in the gym that sparred with Golovkin – he was able to maneuver them and do what he wanted to do."