Cika jumla mai zuwa: A shekara ta 1900, Clarke ya shiga Pittsburgh Pirates a matsayin dan wasa da kuma manajan, rawar da zai rungumi har zuwa lokacin da ya yi ritaya a 1915. An yi jayayya cewa mafi kyawun kakar wasan Clarke ne a yayin da ya jagoranci manyan wasannin a cikin matsakaicin slugging da OPS kuma ya jagoranci National League a cikin sau biyu. Ya gama na biyu ne kawai ga abokin aikinsa, Honus Wagner, don taken buga wasan National League. A cikin
a gasar cin kofin duniya ta farko, Clarke ya buga.265 amma Cy Young na Boston da Bill Dinneen sun fi Pittsburgh gaba daya kuma sun lashe gasar a wasanni takwas.