I dont understand where this "ketchel had an iron chin" stuff comes from. Ketchel could be dropped, hurt, and knocked out. He was carried by Johnson (literally and physically) and the instant Johnson wanted to get rid of him he laid ketchel out with one punch that left him deader than a doornail. Johnson wasnt exactly a huge puncher at HW. What makes you think a legendary puncher who was bigger and more aggressive than Johnson would do anything but destroy Ketchel.
I am a big Ketchel fan,but anyone who watches the fight with Johnson can see that Jack is blatantly holding Stan up whenever he lands solid and wobbles him,and I agree Johnson was not a huge hitter.