PHILADELPHIA – Even as Artur Beterbiev was wearing him down, Oleksandr Gvozdyk’s promoter had him ahead entering the fateful 10th round of their light heavyweight title unification fight Friday night.

“I thought Gvozdyk was winning the fight,” Bob Arum said following Beterbiev’s 10th-round, technical-knockout victory. “You know, close, but winning the fight. Clearly, Beterbiev was coming on in the last two rounds. I thought before the last two rounds, not including the knockout round, Gvozdyk was comfortably ahead.”

Gvozdyk boxed well through eight rounds, before Beterbiev began hurting the former WBC champion in the final two rounds. Gvozdyk (17-1, 14 KOs) still was ahead on two of the three scorecards entering the 10th round at Temple University’s Liacouras Center.

Judges John McKaie (87-84) and Ron McNair (86-85) had Gvozdyk in front through nine rounds. Judge John Poturaj favored Beterbiev, 87-83, entering the 10th round.

In the ninth and 10th rounds, however, CompuBox credited Beterbiev with a 49-8 edge over Gvozdyk in power punches. That accounted for almost all of the difference in CompuBox’s final advantage for Beterbiev in overall punches landed during their fight (161-of-515 to 118-of-614).

Russia’s Beterbiev (15-0, 15 KOs) knocked down Ukraine’s Gvozdyk three times in the 10th round. Referee Gary Rosato stopped their fight at 2:49 of that round, once Gvozdyk went down a third time.

Beterbiev, 34, retained his IBF light heavyweight title and won the WBC belt from Gvozdyk.

“I thought it was a terrific fight,” Arum said. “Gvozdyk was out-boxing him early, and ‘The Beast’ just wore him down and finally took him out. I mean, he’s really one of the strongest light heavyweights I’ve ever seen. Really, he has tremendous energy and takes a great punch, and stays in there and finally wears his opponent out.”

The 32-year-old Gvozdyk impressed Arum as well. He took a lot of flush punches from the rugged Beterbiev, before finally going down in the 10th round.

“It didn’t surprise me,” Arum said. “Gvozdyk is a hell of a fighter, takes a good shot. But if you keep getting hit like that, it wears you down.”

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.