From BR Bullpen

3 is perhaps the most important number in baseball numerology. It is the number of outs in a half inning and the number of strikes require to record a strikeout. There are three numbered bases. Many other important numbers are powers of three (32=9 innings per game and players on a side, 33=27 outs per game, 34=81 home games per season, etc.).

3 was Babe Ruth's uniform number with the New York Yankees, refering to his place in the lineup. As such, it became a much-coveted number for players of other organizations. David Wells wore it in his stint with the Boston Red Sox, as did Alex Rodriguez with the Texas Rangers.

The Yankees' #3 was also worn in the first month of the 1948 season by the immortal Cliff Mapes, who himself allegedly (according to The Sporting News) hit a 500+ ft. home run while playing for the AAA Kansas City Blues. Mapes had the further distinction of being the last player before Mickey Mantle to wear #7, which was first worn by the Mick when he was recalled from the Blues shortly after the All-Star break in 1951.

Notable players who have worn this number[edit]