Why did Ted Williams refuse to sit out and protect his .400 batting average?

Because, in his own words, he wanted to earn it. Entering the final day of the 1941 season, Ted Williams of the Boston Red Sox had 179 hits in 448 at-bats, an average of .39955, which would have been officially rounded up to .400. His manager, Joe Cronin, offered him the chance to sit out, but Williams declined. "If I'm going to be a .400 hitter," he said at the time, "I want more than my toenails on the line." He played both games of a doubleheader, went 6-for-8, and finished 185-for-456, which rounds to .406.

The number he was chasing is simple: batting average is hits divided by at-bats, usually rounded to three decimal places and read without the decimal, so a .300 hitter is "batting three hundred". A .300 season is considered excellent today, and .400 a nearly unachievable goal. No American League or National League player has reached it since 1941; the closest was Tony Gwynn's .394 in 1994. And the rules of the day worked against Williams: in 1941, sacrifice flies counted as at-bats, and under today's rules he would have hit between .411 and .419, based on game accounts from the time.

Despite its fame, batting average has real blind spots. It ignores walks and says nothing about power, which is why sabermetrics, the statistical study of baseball, considers it a weak predictor of runs scored. On-base percentage and slugging percentage were designed to capture those things, and together they form OPS. The definition matters enormously: in 1887, walks were briefly counted as hits, and 11 players batted .400 or better before the experiment was abandoned the next season.