What about catchers, infielders and outfielders? Most never get to throw off the mound and they have some pretty good arms. Do they risk injury because they throw off flat ground? Maybe mounds were built only as a reference point for pitchers so they can find the correct distance to pitch from? Maybe it's a coaching aid. You have to admit It would sound kinda funny to hear a coach say --- "Johnny, I want you to take the flat ground in the opener Friday night". Personally I think it was built so the catcher could have a reference point on his throw downs to second base. Besides, what is three miles an hour when velocity means nothing? Pass the eggnog!
Fungo