BETHLEHEM, PA – They come in dull wisps, each thudding blow lets out another a more audible gasp of air from the poor sparring partner Sergei Kovalev has been feasting on this time.

John David Jackson, Kovalev’s trainer, leans in over the ropes and teases his fighter they’re going to have to start paying their sparring partners more, because they’re not sticking around.

Another leaves before getting paid. He wants no part of Kovalev (20-0-1, 18 knockouts). Few do.

Cornelius White (21-1, 16 KOs) is going to try his luck, and his jaw and his ribs, against Kovalev in a light heavyweight title eliminator Friday night on NBC Sports Network’s Fight Night at the Sands Casino Resort Bethlehem, in Bethlehem, Pa.

Kovalev is arguably one of the hardest punchers in the game today. He’s stopped eight of his last nine opponents, including game former titleholder and contender Gabriel Campillo in the third round in his previous outing. Kovalev is accurate, poised, doesn’t rely too much on his heavy hands and is primed to make a run at newly crowned light heavyweight world champion Adonis Stevenson.

The twist and somewhat scary secret to Kovalev’s power is that he doesn’t know exactly how powerful he is.

“Adonis Stevenson is the most powerful puncher [at light heavyweight], I think,” Kovalev said through a translator, with a straight face. “I’m not kidding. He knocked out Chad Dawson with one punch and no one expected that. That shows me he has knockout power. Someone was ready in that fight and someone was not. For me, it’s not all about the punch. I go into fights not thinking about the knockout. If the knockout comes, it comes. I go into fights to box. I don’t want to look to land that one punch.”

This will be Jackson’s fourth fight training Kovalev (their first together was Kovalev’s two-round destruction of Darnell Boone in June 2012). Jackson likes Kovalev’s precision. He says Kovalev is a far more polished boxer than he gets credit for.

“Sergei has boxing skills, but he hasn’t shown any need for it because when he hits guys, they retreat,” Jackson said. “I told him one day he’ll meet a guy who can take his shot for a while, but until that day comes, he’ll keep knocking guys out. Sergei spars heavyweights; he hits that hard. He has natural power; true punchers are born, not made. His power was there before I arrived.

“Honestly, I don’t think there was much to add to his technique. He’s so precise with his punches that I want to let him do his own thing. I see certain things he can change, but for me, that’s a slow progression. I’ve been doing a lot of fine tuning. He’s one of the few Russian guys that I train that doesn’t rely on his power. When we first got together, he was a little leery of me. They kind of threw us together, and some fighters are more protective of their style. We worked around those things. There is a trust factor between us now.”

Kovalev grew up a fighter. From Chelyabinsk, Russia, in the shadow of the Ural Mountains, where a meteor exploded back in February (and if you go even further back, where the once-Soviet Union built tanks during World War II, calling it “Tankograd”), Kovalev began boxing when he was 11, accompanying a friend who told him he was going to a boxing gym.

“I played hockey growing up, but when the equipment began getting expensive, I started to box,” Kovalev said. “My parents were factory workers growing up. But I grew up fighting all of the time, every day. I never came home with a black eye, though. All the kids fought. I wanted to box because I wanted to see who the strongest kid was. That’s the way it is in Russia.”

Kovalev admits he doesn’t know too much about White, other than he’s rangy and hasn’t faced the kind of opposition he has. Jackson stresses Kovalev can’t overlook White, although the former middleweight titleholder knows the fight everyone wants to see at light heavyweight would be Kovalev and Stevenson.

Jackson knows both fighters well. Before working with Kovalev, Jackson once briefly worked with Stevenson.

“I trained Stevenson for one fight, and unfortunately, it’s the fight Stevenson lost against Darnell Boone,” Jackson said. “I can tell you Kovalev is more technically sound than Stevenson. Stevenson is a devastating puncher and the public would love to see that fight, maybe a year from now. The money would great a year from now. Sergei has to do his thing Friday night. Cornelius is a tall, rangy kid. Any fighter is dangerous inside the ropes.

“Sergei knows he can punch, but we want to make him a better body puncher. There’s more than just going to the head. These guys will fold much sooner. But I’m going to have to start bringing in cruiserweights. We’re getting sparring partners leaving without being paid because they don’t want any part of Kovalev.”

Kovalev doesn’t realize how hard he hits. It’s a testament to how hard he punches.

Photo / Emily Harney-Getty Images