Koufax's strike out totals were better each year.
The question becomes 'Were batters swinging at balls or was Koufax getting call strike three's more often?'.
It would be ironic if the big difference in Koufax's pitching stats improving was in batters swinging at balls, rather than taking walks.
I think a big part of it was just Koufax somehow finally learning to harness his gifts. Since he went straight to the Major Leagues and then was used erratically with no time to learn in the minors, it's almost a wonder that he didn't fail as a pitcher. The bonus rule was cruel in that the very best prospects were offered the most money which then required two years in the Major Leagues and ruined most of them. Koufax, Killebrew, and Kaline were among the few who overcame this destructive rule. Maybe as long as your surname started with a "K" you were safe! 
quote:Originally posted by EdgarFan:
Reminds me of another lefty who took a while to figure it out, but when he did, was something really special. This guy couldn't hit the broad side of a barn when he first came to my home town team - his BB/9 was 7.9 in his first full year here. He turned out okay though.
Couldn't hit the broad side of a Kruk either!
"I became a good pitcher when I stopped trying to make them miss the ball and started trying to make them hit it." –Sandy Koufax