I caught two pitchers who threw 90+ while in college. One played for our team and the other had already graduated and worked out with us getting ready for spring training. Both played mlb. Bruce Berenyi (Reds, Mets) and Dave Wehrmeister(sp) (Padres).
I was a soph (transfered so it was my first year at the school). Wehrmeister asked me to catch him. I said OK. WOW. If they are slightly wild it's a chore.
Here's what happened to my roommate, another catcher, while catching Wehrmeister. (He had caught Rick Sutcliffe in high school and summer ball) He was about 15' in front of a concrete block wall. Wehrmeister let it fly. Went over roommates head and before he could turn to look, the ball hit the wall, rebounded, and hit my roomate in the back of the head.
The heavy fastball that breaks down and in to a right hand hitter is brutal on a catchers thumb. You have so little time that you can't even turn your glove over to catch it. So, you kind of swipe at it and if you catch it just wrong it hits the pad of the thumb and jams it. One of those and it won't go away for the entire season if you keep playing. Any kind of bump reinjures it. Over and over and over.