Thanks. As a japester I’m ridden with self-doubt. I know you’re out there 'cause I can hear you breathing sort of wraps it up, often.
From that link:
Perhaps this answer should be checked by baseball experts in The Game Room.
Certainly at this point the molecular binding energy is insignificant, and the math treats the object as a plasma of atoms. And I doubt that there are any natural processes that could achieve that sort of speed without turning the mass into a plasma.
Well, I certainly think the case could be made for the batter diffusing to first base 
n/m
Why that assumption? Most of the science fiction I’ve read regarding relativistic kinetic energy weapons (as WMDs, essentially) make a point of taking about how long it would take to get to speed. They’re envisioned as interplanetary weapons, perhaps interstellar-range, where you have days or years to get them up to speed using whatever reaction drive technology you have which is capable of getting to relativistic speeds. (Targeting is another issue, but since planets aren’t very maneuverable, a good ephemeris is probably all you need.)
Unless the process were bounded, that’s illegally moving outside the runner’s path.