The fight was much closer than many had predicted until Martinez landed a straight right to the head which floored the 29-year-old and left him unable to rise to for the 10-count.
The 36-year-old Argentine was ahead on all the judgesâ€™ score cards – 99-91, 97-93 and 96-94 – when the bout was ended.
The win gave Martinez his third straight knockout victory, but he was made to look beatable for the first time since becoming the best middleweight because of his opponent’s solid boxing skills.
Barker used his height and reach advantage to keep the champion at bay in the early rounds, breaking Martinezâ€™s nose in the fourth with his solid jab and occasional right hand.
However, from the fifth round onwards Martinez increased his work rate and soon began overwhelming his opponent.
The Argentine fought behind rapid four and five punch combinations which Barker was unable to do deal with, forcing him cover up behind his gloves for long periods of the later rounds.
The Londoner’s punch output decreased with every round as Martinez became stronger and undoubtedly sensed his opponent’s inability to keep up with the pace.
And as the bout entered the final rounds, it was evident that Barker was looking to survive rather than win. The British challenger was not throwing enough punches to be in with a realistic chance of the winning the bout.
Martinez then showed his championship class by improving as the fight progressed, and as the 11th round began the only way the Argentine could lose was if he allowed himself to be knocked out.
The final blow, a straight right to the side of the head, seemed to unbalance Barker more than anything, but he was still on the canvas as the referee counted to ten.
â€œI canâ€™t remember the punch,” said Barker after the fight. “My legs just fell out from under me. I was trying to get up, but couldnâ€™t, I didnâ€™t feel he was a massive puncher before that.â€
Amid continued speculation of a potential fight against Manny Pacquiao or Floyd Mayweather Jr, Martinez said: â€œIâ€™ll fight anybody, as long as I can come to a good deal and so can my rival.â€
Martinez’s record now stands at 48 victories, 27 by knock out, two losses and two draws.
Barker, suffering defeat for the first time, saw his record fall to 23 wins, 14 by knock out and a single defeat. However, his reputation and stature have greatly improved despite the loss.
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