In 1900, Clarke joined the Pittsburgh Pirates as a player and manager, roles he would embrace until his retirement in 1915. was arguably the best hitting season of Clarke's career as he led the Major Leagues in slugging average and OPS and led the National League in doubles. He finished second only to his teammate, Honus Wagner, for the National League batting title. In the first World Series, Clarke hit .265 but Boston's Cy Young and Bill Dinneen outpitched Pittsburgh overall and won the series in eight games.