Amir Khan is convinced he possesses one of the best chins in boxing after standing up to full shots from pound for pound king Manny Pacquiao.

Khan faces Zab Judah in Saturday night's light-welterweight unification showdown at the Mandalay Bay Resort admitting many still question his punch resistance.

Even a thrilling clash with knockout specialist Marcos Maidana, which saw Khan survive a ferocious battering in the 10th round to triumph on points, has failed to appease his critics.

It is exasperating for the 24-year-old from Bolton, who insists he repeatedly displays his warrior spirit during sparring sessions under the guidance of trainer Freddie Roach at the Wildcard gym.

Among those testing Khan's resilience is Filipino great Pacquiao, who has failed to floor his stablemate with his best punch.

"Freddie has to tell me to calm down in training," said Khan.

"In sparring when I get hit with a clean shot by big guys who are 154 pounds, I get straight back at them. That's my style.

"I want to show them they haven't hurt me and if they do catch me, it's the worst thing they could do because that's when I turn on.

"Sparring at the Wildcard is like a fight, it's not a spar. We throw full-on power shots.

"I pay my sparring partners a lot of money and because they're in Freddie Roach's gym, they're out to prove how good they are.

"I've proved I've probably got one of the best chins in the boxing business. I've been hit with huge shots in sparring.

"Manny's hit me with a clean back hand, his hardest shot, and I walked straight onto it and still stood there.

"He was asked if I have a glass jaw and he said 'what are you talking about, I spar with him and he's knocked lots of sparring partners out who are heavier'.

"And we fight hard in sparring with 12 or 14 ounce gloves, not big, big gloves."

The seeds of doubt over Khan's vulnerability were sown well before he was flattened in 54 seconds by Breidis Prescott in 2008.

Earlier visits to the canvas against the light punching Willie Limond and Michael Gomez had pointed to a fragility that was brutally confirmed by Prescott.

The defeat resulted in the appointment of Roach, who has since guided the WBA champion to seven successive victories, including the notable scalps of Marco Antonio Barrera, Paul Malignaggi and Maidana.

With his defence tightened and greater strength developed in his lower body to provide a solid base from which to soak up punishment, Khan now appears a more durable fighter.

Under Roach he has yet to be knocked down but still he is forced to defend himself, though he insists the perception of his weakness has its benefits.

"People are still talking about my chin and crap like that, but let them think that," he said.

"That way it puts it in their mind that I might get knocked out. It's a good thing, makes it more interesting.

"Since I was knocked out I've taken big shots and have never been down again. But if people think I'm chinny it works in my favour.

"It keeps me training harder to prove a point to people and gets them excited to watch me fight. And people know Zab Judah has the power to knock people out.

"If I hadn't been knocked out by Prescott, people would have thought 'this guy's always going to win'.

"But people buy a fight on pay per view because it will be exciting and there may be knockdowns.

"Fighters don't think I'm chinny, you just get a few fans who think like that.

"As long as I keep winning and climbing the ladder they can say all they want."

Victory over five-time world champion Judah, who holds the IBF belt, would be another impressive scalp for a fighter who has his heart set on replacing Pacquiao as the next pound for pound king.

Even at 33 Judah is a dangerous opponent having fought Floyd Mayweather, Miguel Cotto and Kostya Tszyu, though he lost of all three among six defeats in 49 contests.

"Judah has been a good champion, but he's had his time and it's my time now. I'm the young one and I'm going to take his belt," said Khan.