Don't really understand this question, given that having a good chin is one of the most important attributes in order for a fighter to be successful. It's like saying what if Mayweather had power?
I don't think so. I don't think chins are like that. If you throw a punch and are reckless and leave it out there as you are trading, you will not take a punch well and Khan just leaves his chin out there.
not like Khan. He has a lapse in concentration which makes his chin very vulnerable. If he thought more about picking his shots and being economical he could tighten up when the punches come.
If he had the chin that fellow speedy welter legend Ray Leonard had vs Hearns and Duran he still would have been exposed at that level by elite fighters, Ray beat Hearns in the pocket Khan always clinches up close like Lewis did vs Tyson.
His speed (hand and foot) is between A+ and straight A, maybe on a bad day kissing the line between A minus and B+. (depending on whether moving forward, laterally or in reverse and whether firing pot shots or combos) His chin is actually no worse than a B-, despite all the fun we have at his expense. His defense however (aside from his movement, so he's basically the same as someone like Adonis Stevenson in this respect, where if you take away his ability to outspeed foes it turns out the emperor has no clothes ...and no tight quarters defensive game) is a C flat. His ring IQ on his best day never rises above D+. And even his power is a little overrated. To hear any of his crazy fans tell it he's somewhere in the A range. More like a straight B...and that's at welter. Less the higher up he goes. Fundamental boxing skills are somewhere in the mid to high B realm, if you're being generous. Absolutely not A material.