LAS VEGAS – Robert Helenius proved Saturday night that his first stoppage of Adam Kownacki wasn’t a fluke.

The 37-year-old Helenius basically beat up a defenseless Kownacki throughout their rematch, until referee Celestino Ruiz determined that Kownacki shouldn’t continue during the sixth round of their scheduled 12-round heavyweight fight at T-Mobile Arena. Ruiz deducted a point from Kownacki for low blows in the fifth round and halted their one-sided rematch in the sixth round because Kownacki, whose left eye was swollen shut, had taken too much punishment on the Tyson Fury-Deontay Wilder pay-per-view undercard.

Finland’s Helenius improved to 31-3 and produced his 20th knockout by stopping Kownacki again. Brooklyn’s Kownacki (20-2, 15 KOs) has lost only to Helenius.

“It was good,” Helenius said. “Either way, it would have been a stoppage. I had a lot of good shots tonight and he didn’t have any. I expected it because what does he have? Don’t get me wrong – he’s a good brawler, but I’ve been fighting brawlers for 20 years. I know how to deal with them, even if they are hitting me low or behind the head. That doesn’t bother me.”

CompuBox’s unofficial punch stats reflected Helenius’ dominance. According to CompuBox, Helenius landed 129-of-366 punches overall, 77 more than Kownacki (52-of-270).

The 32-year-old Kownacki was a 2-1 favorite entering their rematch, according to Caesars Sportsbook, despite that Helenius dropped and stopped him in the fourth round of their first fight. Kownacki was winning their initial meeting pretty easily through three rounds, but Helenius hurt him badly during the fourth round of their March 2020 bout at Barclays Center in Brooklyn.

Helenius scored one official knockdown and referee David Fields missed another knockdown before Fields stopped their scheduled 12-rounder with Kownacki still on his feet.

The round before their fight ended, Ruiz deducted a point from Kownacki for another low blow 41 seconds into the fifth round. Helenius hammered away at Kownacki in the final minute of the fifth round, a sequence that began with a right uppercut that rocked him.

With just over a minute to go in the fourth round, Helenius landed a right to Kownacki’s body. Kownacki also winced numerous times during the fourth round because he was having trouble seeing out of a left eye that was swollen shut.

A right-left combination by Helenius wobbled Kownacki late in the third round. Several seconds later, Kownacki landed a low blow that caused a brief break in the action.

By the start of just the second round, Kownacki had to deal with severe swelling surrounding his left eye. Kownacki had more success in the second round than a difficult first round, but he still took several flush punches while attempting to smother Helenius.

Helenius made Kownacki retreat by blasting him with a left uppercut just 35 seconds into their fight. That shot seemed to rock Kownacki, but Helenius didn’t follow up on it.

With about 30 seconds to go in that opening round, though, Helenius drilled him with a right hand that buckled Kownacki’s legs. Helenius did try to finish off Kownacki in that instance, but Kownacki made it to the bell.

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