He became full-time Recreation Director after Sharp's retirement. The title was later changed to Jamestown Parks, Recreation and Conservation Director and entailed supervising about 20 youth baseball leagues, all recreational sports for boys and girls in the city and several adult programs. In the 1970's he was assistant general manager, with Eric Gougin, of the Jamestown Expos of the New York-Pennsylvania League and is a past director of the league.
Diethrick is a past district commissioner of the Amateur Softball Association of America, was tournament chairman for the Middle Atlantic Regional Babe Ruth Tournament and the first two 13-year Old Babe Ruth World Series which were held at College Stadium.
He became a member of the National Babe Ruth Baseball Advisory Board and was inducted into the Babe Ruth League Hall of Fame in 1997.