On August 6, 1983 — Eric Rasmussen throws a 4-0 shutout against the Red Sox in his first American League outing. The Royals starter, who also blanked the Padres as a Cardinal in his first-ever major league game in 1975, becomes the first pitcher to toss a shutout in both his National League and American League debuts.

Source:
Baseball Reference August 6
National Pastime
Retro Sheet
Hall of Fame
SABR Games Project
Replay The Game