NEW YORK – Anthony Dirrell never saw the shot that could send him into retirement coming.

Neither did anyone else at Barclays Center.

Caleb Plant violently ended their otherwise unremarkable bout between former super middleweight champions with a counter left hook that knocked Dirrell unconscious Saturday night on the Deontay Wilder-Robert Helenius undercard. Referee Harvey Dock immediately waved an end to their fight, at 2:57 of the ninth round, as Dirrell lay motionless on the canvas.

Plant (22-1, 13 KOs) hadn’t done anything to affect Dirrell with his punches to that point in the bout, but he drilled Dirrell with a perfect punch that knocked out an opponent that had repeatedly expressed his hatred for Plant prior to their scheduled 12-round fight. The former IBF 168-pound champion motioned as if he were shoveling dirt on Dirrell (34-3-2, 25 KOs) before Dirrell regained his senses and was helped to his feet.

David Benavidez stopped a bloodied Dirrell in the ninth round of their WBC super middleweight title fight in September 2019 at Staples Center in Los Angeles, but Dirrell’s corner requested that stoppage. This was a much more devastating defeat for the 38-year-old Dirrell, particularly due to the animosity between him and Plant.

The 30-year-old Plant, of Ashland City, Tennessee, hadn’t fought since Canelo Alvarez knocked him out in the 11th round of their full 168-pound title unification fight last November 6 at MGM Grand Garden Arena in Las Vegas.

Dirrell ended an 11-month layoff as well. The former WBC super middleweight champion hadn’t boxed since he viciously knocked out Marcos Hernandez in the fourth round on the Alvarez-Plant undercard.

Before Plant stunningly ended their fight, Dirrell drilled Plant with a right hand that moved Plant backward approximately 30 seconds into the ninth round. Plant landed a jab with just over 1:40 on the clock in the ninth round.

Dirrell switched to a southpaw stance to try to throw off Plant near the midway point of the eighth round. Plant pushed Dirrell to the canvas later in the eighth round, immediately after Dirrell connected with a right hand.

Dirrell taunted Plant for not engaging once fans booed after the midway mark of the seventh round. Plant caught Dirrell with a counter right just before the bell sounded to end the seventh round.

A left hook by Plant moved Dirrell backward about 40 seconds into the sixth round. Dirrell mocked Plant by literally running away from him just before the sixth round ended.

A jab by Plant knocked Dirrell off balance about 20 seconds into the fifth round. Plant’s left hand backed Dirrell into the ropes with approximately 30 seconds remaining in the fifth round, but Dirrell pounded his gloves together and walked forward.

Dirrell went on the offensive and landed a right hand as the fifth round came toward a conclusion.

Dirrell countered Plant with a right hand after Plant missed with a left with a toward the end of the fourth round. Another right hand landed for Dirrell just before the fourth round ended.

Plant and Dirrell tumbled to the canvas after an awkward entanglement with just under 45 seconds on the clock in the third round.

Dirrell landed a right hand in the middle minute of the second round, which drew a response from the crowd. Dirrell appeared to clip Plant with a right hand that made Plant retreat as they neared the end of the first round.

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