I think I wasn't precise with my post, I was simply talking about the point in general. There's no way to quantify "mental preparation" though I'd assume the top levels of any sport require a huge amount. Sherman is the best at what he does in the top league of the sport he plays, he has no way of knowing what it's like for Trout or Djokovic.
I like Sherman. He's not an idiot and doesn't tolerate stupid media members.