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The 30-year-old Argentine put his foot on the gas from the first bell, forcing Broner to eat a couple of stiff shots before eventually sending the American down for the first time in his career in the second.
Somehow, the 24-year-old managed to survive, but he was hanging on for dear life as Maidana pressed forward relentlessly.
The challenger had built a healthy lead before Broner began to work himself into the bout, but the champion was down once again in a crazy eighth round that saw Maidana later deducted a point for a headbutt.
Time and time again Broner escaped reprimand for constant clinching, pushing and even a punch after the bell at the end of the 11th.
It was fitting that a truly epic war went into a final round, but when the bell sounded, 'The Problem' knew that he had been well beaten - although he had done well to take everything Maidana could throw at him.
All three judges scored the bout unanimously in favour of 'El Chino', returning cards of 115-110, 116-109, 117-109.