NEW YORK – Joe Smith Jr.’s longtime promoter applauded Artur Beterbiev’s superb performance Saturday night.

As precise as the powerful Beterbiev was with his punches against Smith, Joe DeGuardia nevertheless noticed that the unbeaten IBF/WBC/WBO light heavyweight champion continued to land shots on the back of Smith’s head. Smith’s team asked referee Harvey Dock to be mindful of Beterbiev’s prohibited rabbit punches prior to their 12-round, 175-pound title unification bout at Madison Square Garden’s Hulu Theater.

Dock warned Beterbiev for hitting Smith behind his head with 1:20 to go in the second round. Beterbiev appeared to land several right hands to the back of Smith’s head in the first round, and the final punch with which Beterbiev connected caught Smith behind his head.

“I’ve never seen Joe hurt like that,” DeGuardia told BoxingScene.com. “And again, you know, obviously I give Beterbiev credit. He’s a real fighter and a skilled, precise fighter. But we spoke to the referee beforehand. We didn’t like the idea of shots on the back of the head. We were concerned about that. I mean, I saw the last punch was on the back of the head. I saw a couple before. I know the referee warned him once, but you know, look, all in all, you can’t take anything away from Beterbiev. He’s a great fighter.”

Montreal’s Beterbiev (18-0, 18 KOs) sent Smith (28-4, 22 KOs), of Mastic, New York, to the canvas with right hands very late in the first round and again 38 seconds into the second round. The first right hand that dropped Smith landed on the top of his head, whereas the second right that floored him connected to the side of his head.

Beterbiev blasted Smith with a left uppercut and a right uppercut before his right hand landed to the back of Smith’s head and wobbled him with 45 seconds remaining in the second round. Smith remained on his feet after taking those three shots, yet that’s when Dock determined Smith shouldn’t continue.

“We knew going into the fight you’ve got two punchers and anything could happen quickly,” DeGuardia said. “A lot of analysts said, and they had a right, whoever’s gonna hit first and get that right shot in first, you know, could set the whole fight. And that’s really what happened. I think if Joe lands one of his punches or bombs, it’s a different story. But Beterbiev landed. You know, that’s it.”

The 37-year-old Beterbiev became the first fighter to conventionally stop Smith in a professional bout. The first technical-knockout loss of Smith’s career came in August 2010, when the former WBO champion couldn’t continue in the fourth round against Eddie Caminero due to a broken jaw.

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