After suffering the third knockout defeat of his career, Matchroom boss Barry Hearn believes Amir Khan "was never a great fighter" and should quit boxing for the sake of his health.
The 29-year-old fighter was unable to cope with the step up in weight, after being stopped by middleweight Saul Alvarez earlier in the month, and has subsequently admitted he will return to the 147lbs division.
However, Hearn believes the Lancastrian should retire from the sport, after 31 careers wins - 19 by knockout - and four defeats, while also ending speculation of any chance that Khan will meet his bitter rival, Kell Brook, in the ring.
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Hearn told Sky Sports: "Listen, the guy has been knocked out at lightweight, he's been knocked out at light-welterweight, now he's been knocked out at middleweight - and he's deciding who he'll want to fight?
"He should retire. He should retire for his own health. These people won't listen."
Khan was, worryingly, left on the canvas after Alvarez condemned the Brit to a sixth-round knockout in Vegas - unable to move after the Mexican dealt him the decisive blow - and Hearn admits the Bolton-born fighter would not stand a chance of defeating Brook.
"He says he's got three or four fights left in him. Does that mean three or four times he's going to get knocked out?" said Hearn.
"Because if he fights Kell Brook, he gets knocked out, and he knows that as well. We all know that."
"It's a fight that we would all have loved to have seen, but frankly it's gone past it's sell-by date and Amir Khan has gone by his sell-by date as well. The only person who doesn't know it, is Amir Khan."
The former WBA Super World Super Lightweight and WBA Super Lightweight champion is considering facing Danny Garcia for the WBC world welterweight title, as the Philadelphian's mandatory challenger.
But Hearn feels Khan has damaged his reputation by taking on one of the middleweight division's best boxers, and that the Brit would be an easy fight for Garcia, who knocked out Khan inside four rounds in 2012.
"He was never a great fighter, but he was a good fighter, and it's sad when you become an opponent," said Hearn.
"The only people that will box him, Danny Garcia maybe, because they are looking for an easy fight and Amir's an easy fight."
Khan has previously admitted he is happy to face any willing opponent, but his step up to the middleweight division could, seemingly, have had a major impact on his career. Although he is adamant it is not yet time to hang up his gloves.
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