The baseball world didn't fully embrace the importance of on-base percentage and come to understand its value relative to batting average until much later. While .406 remains an astonishing number, Williams' .553 OBP in '41 stands out as the more impressive of the two.
Of course, Barry Bonds' late-career performance skewed the single-season OBP leaderboard -- as it did for most offensive stats. The Giants slugger posted at least a .515 OBP every year from 2001-04, breaking Williams' record in '02 (.582) and then topping himself during his absurd '04 run (.609, with a mind-boggling 120 intentional walks).
But set Bonds' exploits aside, and Williams stands alone.
Prior to '41, John McGraw held the single-season OBP record (.547 in 1899) and Babe Ruth owned the modern record (.545 in 1923). From 1901 through 1940, only Ruth (five times) and Rogers Hornsby (once) had produced an OBP of at least .500.
Then came '41, which was Williams' age-22 season. He played 133 games in which he went to the plate at least twice, and he reached base safely at least once in all but three of those. In more than 80 percent of them, he reached multiple times. From July 20 through the end of the regular season, Williams put together a 68-game on-base streak in which he recorded a .420/.591/.816 batting line with a BB/K ratio of 88-to-16.
Teddy Ballgame led the Majors in almost every major offensive category that year, and his .553 OBP was 101 points higher than that of his closest challenger. Williams' feat was far from a fluke. From 1940-58, he twice paused his career for military service but led the AL in OBP in each of the 12 seasons in which he played at least 100 games.
Post-'41, Mickey Mantle is the only other player to have reached base safely in half of his plate appearances -- with a .512 OBP in '57. Otherwise, Williams' closest challengers have been Norm Cash in '61 and Frank Thomas in the '94 strike year -- both at .487. Bonds, Mantle, Cash and Thomas are the only players during that time to have a season with an OBP better than Williams' career mark of .482, which is an all-time record.
Moreover, nobody other than Bonds has even put together a first or second half with an OBP of .553 since Williams retired. Joey Votto came the closest when he posted a .535 mark after last season's All-Star break.
Although the number .553 may never hold the same cachet as .406 in baseball lore, Williams' on-base achievement certainly stands out more now than it did in '41.