An interesting story regarding Ty Cobb and Walter Johnson. At first, Cobb was like everyone else: he couldn't hit the Big Train (Johnson's nickname). Then one day, Cobb found a weakness: Johnson was afraid of his own speed. He was very afraid of hitting a batter and killing him.
Cobb started crowding the plate, even overhanging the inside corner with his head and elbows. Johnson pitched everything outside to avoid hitting him. Cobb was able to get ahead in the count, then back away a little bit, and take advantage of the pitch that had to be just a little more over the plate.
Cobb batted over .320 lifetime against Johnson, exploiting this one "weakness."