Khan has lost three bouts in his career, two of those coming via knockdown. Most would consider it the Brit's biggest weakness, given that his boxing skills, which led him to a silver medal at the 2004 Olympics, and world titles at light welterweight in the professional ranks are excellent.
But Khan's tweet suggests his chin compares favourably with some of the greats of the fight game, including Ricky Hatton, Mike Tyson, Arturo Gatti and Kostya Tszyu.
Does he have a point? On facts alone, certainly—but when you look into the stats in slightly more detail, a fuller picture emerges.
For example, Hatton did lose three fights by way of knockout, but two of those were to Mayweather and Manny Pacquiao—indisputably the very, very best boxers he could have fought at the time.
The third was his last, when Hatton ignored the advice of many in boxing to mount a comeback after three-and-a-half years out of the ring. He was a shadow of his former self.
The majority of Tyson's defeats also took place at the end of his career, by which time his focus on the sport had long since faded.
Khan's knockout losses came at the hands of Breidis Prescott, who has lost five fights since that stunning Round 1 win, and Danny Garcia, whose victory over Khan was, by some distance, the most significant of his career at that stage.
Khan was also knocked down in his previous bout against Julio Diaz, although on this occasion he showed strength and resolve to come through and win on points.
Mayweather had a poll to let fans decide which boxer he should fight next, and Khan appears to have beaten Marcos Maidana in that particular head-to-head, according to BoxRec News (h/t Yahoo Eurosport).
But few fans give Khan a chance of beating Mayweather should the pair meet in the ring on May 3.
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