On Sept. 30, 1956 at age 16, the White Sox Jim Derrington became the youngest pitcher to start a game when he faced the Kansas City A’s in the season-finale.
The left-hander, on the roster because of bonus rules of the day, gave up five earned runs on nine hits in six innings in taking the loss.
Injuries curtailed the career of one of the pitching phenoms of his generation. This is a good piece on the Californian. http://articles.latimes.com/1991-06-29/sports/sp-1325_1_major-league/3