British super middleweight Callum Smith has explained that Canelo Alvarez began to target his left arm in the very first round.

On Saturday night, Canelo dominated Smith over the twelve round distance to capture the WBC, WBA super middleweight titles at the Alamodome in San Antonio, Texas.

Smith, who two years ago won the World Boxing Super Series tournament with a knockout of George Groves, suffered his first career defeat.

In the aftermath of the fight, the bicep/tricep area of Smith's left arm was severely swollen. Smith will reportedly underdgo surgery on the arm.

After the first round, Smith explains that he advised his head trainer, Joe Gallagher, that Canelo was targeting his left arm with right hooks.

"It was intentional. I knew from the first round that. I said to Joe in round one, 'He's aiming for my arm.' Every right hook he was throwing, he was going for my arm. And then I think I said to Joe in round four or something, 'My arm is f--ked,'" Smith told Boxing Social.

"It kind of took away my catch left hook, which is my best shot. And whether that was a plan on their behalf, it worked a treat. Because when he was throwing - I remember [George Groves] threw a couple of hooks against me and I thought, 'Well, you're throwing the right hook. The next one you're getting it.'

"And the next one, I countered. If you had told me that Canelo was going to throw that many right hooks at me, I probably would've thought that I would've been able to get my catch-hook counter off. Some people asked afterwards because they thought my hand was hurt because of someone throwing so many right hooks and for me not to return it.

"But when it was hitting me in the arm, it was kind of making my arm drop rather than being able to return with it. But I still jabbed with it, do you know what I mean? It didn't completely take away the game. But it just took that one shot away from me. And I'd say credit to him, I think he knew what he was doing. In the twelfth round, he looked at the swelling and laughed and asked, 'Is it sore?' It's experience on his behalf. It completely tools away probably my best shot.

But, Smith is realistic and believes he still would have lost the fight with both hands available to him. He admits Canelo was just too good of a fighter to overcome.

"It's not an excuse. If I would've had two hands the whole fight, would I have won the fight? Probably not. He was just a little bit too good for me on the night," Smith said.