James Thompson "Doc" Prothro Sr. (July 16, 1893 – October 14, 1971) was an American infielder and manager in Major League Baseball (MLB). Prothro was so nicknamed because he was a practicing dentist before signing his first professional baseball contract at age 26.[1] After playing five seasons in MLB, Prothro became a manager, compiling what remains the worst career winning percentage among major league managers.
In 1939, Prothro replaced Jimmie Wilson as manager of the Philadelphia Phillies. In his three full seasons (1939–1941) at the helm of the Phillies, the club remained locked in the National League cellar — losers of 106, 103 and 111 games. Prothro's career mark of 138–320 has the lowest managerial winning percentage, .301, in major league history.[3][a]
Prothro was fired after the 1941 season and replaced by Hans Lobert and thereafter returned to the Southern Association, where he piloted the Chicks from 1942 to 1947. After he retired as Memphis' manager, he remained active as a co-owner of the club.