Satchel Paige, who made his debut for the Cleveland Indians in July 1948, two days after his 42nd birthday. He was also the oldest player ever, pitching his last game in 1965 at age 59, and allowing only one hit over three innings. [There's some dispute about his exact birthday - he may have been as much as six years older than the above figures!] It maybe nitpicky but I always thought Satch was the oldest rookie and oldest player to play in mlb...
