NEWARK, New Jersey — Damian Knyba beat up Marcin Siwy until a ringside doctor determined Siwy shouldn't take any more punishment Saturday night.

Referee Harvey Dock declared Knyba the winner by technical knockout after the eighth round of an entirely one-sided heavyweight fight on the Vito Mielnicki Jr.-Kamil Gardzielik undercard at Prudential Center. Siwy was bleeding badly from a cut over his left eye and Knyba battered him to head and body throughout their bout between unbeaten Polish heavyweights.

Knyba, of Bydgoszcz, Poland, improved to 16-0 and recorded his 10th knockout. He was disappointed not to stop Siwy sooner, but Knyba suffered a cut over his left eye in sparring a week before they fought and was wary about that wound opening up in their fight.

Siwy, of Czestochowa, Poland, dropped to 25-1-1 (12 KOs).

“I think I could’ve done a bit better, but overall I’m not mad about it,” Knyba told The Ring. “It was solid. It was very easy for me in there. I got injured very shortly before the fight and it was tough to overcome. But I wanted to fight anyway. I wanted to be in here and nothing was gonna stop me.”

The 6-foot-8, 254½-pound Knyba worked mostly off his jab, fought from his preferred range and occasionally connected with right hands. Siwy tried to force his way inside, but it was difficult for him to land any consequential punches because Knyba blocked a lot of his left hooks with his right glove.

By the eighth round, Knyba sensed Siwy was ready to be knocked out and unloaded various head and body shots on his bloodied, beaten opponent. Siwy’s toughness kept him on his feet until the bell sounded to end the eighth round, though.

Knyba’s right to Siwy’s body hurt him toward the end of the seventh round and made his battered opponent move away from him. A left hook to the body by Knyba affected Siwy earlier in the seventh round.

Knyba nailed Siwy with an overhand right that backed him up in the opening minute of the sixth round. Siwy bled from a cut over his left eye at that point and appeared tired.