It seems that to be a hitting coach for most mlb teams you have to have been drafted, then have a big BUT.
"He was picked 12th BUT only played one year in the majors"
"He had a low batting average BUT did walk a lot"
"He only played 6 months in the majors BUT did spent 90 years in the minors."
"He hit 69 home runs BUT....."
Of course I am exaggerating a little bit.
Where does Mark McGwire fit into your list?