MARK TWAIN ABOUT THE JEWISH PEOPLE, published in the year 1899:

[argyl]

5. Sandy Koufax. As great a MLB pitcher that ever lived.

If arthritis in his left arm hadn't cut his career short he'd be the GOAT, no doubt.
He had a five year period with the Dodgers from
1962 to 1966 that I doubt will ever be equaled in baseball.
I've read that after his first unremarkable years with the Dodgers someone, I don't remember who, simply told him to lighten up a little and enjoy what he was doing a little more.
That was after the '61 season. And the next five years are baseball history.
Sandy's 85 y.o. now and lives in Vero Beach, Florida. And he still looks pretty darn good. Tanned and slender.