In a group of 25 people (such as a baseball club), there is a 57% chance that at least two people will share a birthday. In a group of 50 people (such as competing ballclubs), there is a 97% chance of at least two people sharing a birthday. Given this, how often have opposing pitchers shared a birthday?
With the Retrosheet database providing the AL/NL starting pitcher logs through 2014, we have pitching matchups for roughly 200,000 games. The Lahman Baseball Database has complete birthdates for approximately 18,100 players (97% of all in history). A match of the Retrosheet player IDs for both pitchers in each game with the ID (and birthdates) in Lahman yields the following:
- There have been 445 instances of both pitchers sharing the same birthday (month/day only).
- The first occurrence happened April 18, 1911, when Jack Rowan of the Phillies faced off against Al Mattern of the Boston Rustlers. Both gentlemen were born on June 16th, albeit in different years.
- The most frequent match-up of shared birthday pitchers is the 14 by Tommy Bridges and Hall of Famer Ted Lyons between 1932 and 1942. Bridges and Lyons were each born on December 28th, six years apart.
- On May 12th of 1993, the Expos’ Chris Nabholz faced off against the Marlins’ Charlie Hough. Nabholz was born on January 5, 1967 and Hough the same day in 1948. The 19-year differential is the largest age difference between same birthday pitchers.
- January 5th is the birthdate with the most different pairs of same birthday pitchers (7):
- There have been 16 pairs of opposing pitchers who shared the same birthdate, including year:
|Game date||Birth Month/Day||vteam||vlg||hteam||hlg||Vis Name||Vis Birth Year||Home Name||Home Birth Year|