[Bloody Sam Roberts]

I can still throw a 70 mph fastball across home plate.

I don't doubt you. But Home to 2nd base is twice as far and throwing it as hard and fast as you can.
I ruined my cuff by doing that very thing with a baseball when I wasn't prepared for it...backing up the catcher trying to nail the runner headed for 2nd.

[G Larry]

ya...but the right sized rock would still be going 50 mph at 2nd base.

...as it would have exceeded 70 at the half way point.