Punch resistance deteriorating.

[daggum]

This is probably the best most recent example.

before guerrero had a iron chin, thurman put a crack on it. and since seems like guerreo been getting dropped by everyone.

floyd ruined him. he was on an amazing run of fighting bums from 126 to 147 before floyd cherry picked him off

[Combat Talk Radio]

Not sure exactly why, but when Macho Camacho absolutely destroyed Sugar Ray Leonard, a guy who'd NEVER been knocked out or stopped up to that point....

[elfag]

some guys chins got better.

foreman's chin was better in his second career, it was iron.

cotto had a weaker chin at 140 and was hurt bad by torres. At 146/47 with the extra weight he took beatings from manny and margarito.

Canelos chin has gotten better as well, he hasnt been hurt since Hatton

[Dip_Slide]

off the top of my head

Roy Jones after Antonio Tarver
Fernando Vargas after Felix Trinidad

[REMOVE SHARK 55]

Timothy Bradley is up there with Robert Guerrero as the most modern examples of fading punch resistance. I actually think Provodnikov gave Bradley some type of neurological injury which played a part in his early retirement.

[Slyboots]

Juan Manuel Lopez comes to mind. After that Mtagwa fight, he just didn't look right taking shots anymore.

I noticed it during the Rafael Marquez fight, then along came Salido and he straight up shattered his chin.

[Butt stuff]

Not quite the same but once Ortiz was broken once, he never held up past that- and he had a war with Berto the first time round.

[Robbie Barrett]

To be fair, Pacquiao hit him with an absolute bomb.

The finishing punch was a great shot but the punches in the first round were nothing special.

Tszyu, Collazo and the ring post destroyed Hatton's chin. He was almost KO'd by Lazcano before Pacquiao got to him.