Unified light heavyweight king Artur Beterbiev (20-0, 20 KOs) defended his WBC/IBF/WBO world titles with a seventh-round TKO win against former world champion Callum Smith (29-2, 16 KOs) Saturday evening at Videotron Centre in Quebec City, Canada.

Beterbiev remains boxing’s only world champion with a 100 percent knockout ratio by handing Smith his first knockdown and stoppage loss.

The 38-year-old wrecking ball, who calls Montreal home, looked to quickly remove the ring rust following a one-year layoff by chasing down Smith in the opening seconds. Smith, with significant reach and height advantages, tried to land from the outside.

In rounds three and four, Beterbiev began mauling Smith by landing vicious punches around his guard. He boxed from the outside in round five but resumed his forward momentum in the sixth, forcing an increasingly bruised Smith against the ropes to land chopping right hands.

In the seventh, Beterbiev countered a Smith jab with a looping right hand that wobbled him, eventually dropping him with a relentless fusillade of punches. Smith got back to his feet, but he was knocked down again. This prompted head trainer Buddy McGirt to stop the fight at 2:00 mark of round seven.

Beterbiev said, "It’s because of luck. It’s my coach. My team works hard with me, too. Maybe that’s why, too. But I think it’s because of luck.

"We had a couple strategies. We always have more than one. We need to be prepared for several strategies. He gave me a good fight. He stayed strong. Thanks to him. Today, luck is on my side."

Now he hopes for an undisputed fight with WBA champion Dmitry Bivol.

“Yes, of course [I want the Bivol fight]. I need another belt. It would mean a lot to me," Beterbiev said.