Joe Smith Jr. admits he could never implement his strategy to the fullest extent during his short-lived tussle with Russian puncher Artur Beterbiev.

Smith, the Mastic, Long Island, native was stopped by Montreal-based Beterbiev in two rounds in their 175-pound unification bout last Saturday night at Madison Square Garden’s Hulu Theater in New York City. Beterbiev, who went into the fight with the WBC and IBF belts, knocked the typically durable slugger three times before referee Harvey Dock waved the fight off. The win rewarded Beterbiev with Smith’s WBO belt, giving him three of four major titles in the division. Dmitry Bivol owns the other remaining belt (WBA) in the division.

In a sobering assessment posted on his Instagram account Monday afternoon, Smith said he lost his “focus” after absorbing a punch from Beterbiev that he says landed behind his ear.

“I would like to start off by saying thank you to everyone who supports me and my career, I enjoy fighting for each and every one of you,” Smith wrote. “This past weekend did not go as planned as I lost my focus on the game plan after making a mistake that led me to getting caught behind my ear knocking off my equilibrium that I could not recover from.”

It is not exactly clear which sequence Smith was referencing. Smith may have been referring to the right hand from Beterbiev that led to the first knockdown in the fight. In the opening round, Beterbiev, 37, was sliding to his right as Smith, 32, was inching forward, when the Russian exploded with a right-hand counter that seemed to land around Smith’s left temple.

To Smith’s point, midway through the second round, referee Harvey Dock issued a warning to Beterbiev for hitting Smith behind his head.

Smith’s co-promoter, Joe DeGuardia, expressed to BoxingScene.com after the fight that they had informed referee Dock before the fight to be aware of Beterbiev’s “rabbit punches.” DeGuardia said Beterbiev’s last punch landed behind Smith’s head.

“No excuses I should have took a deep breath, relaxed and got back to boxing,” Smith continued. “I just wanted to fight which lead me into the same traps.

“I would have loved to bring home all the titles for you all. I am going to take some time, stay in shape and decide what the future holds for me.”

This is the second time that Smith (28-4, 22 KOs) has come up short in a world title situation.

For his next outing, Beterbiev (18-0, 18 KOs) is expected to face his WBO mandatory, Anthony Yarde, in London in the fall, according to his promoter Bob Arum.