Complex sentence: As a player, La Russa made his major league debut in 1963 and spent parts of five major league seasons with the Kansas City/Oakland Athletics, Atlanta Braves and Chicago Cubs.
Split into simpler sentences: As a player, La Russa made his major league debut with the Kansas City Athletics in 1963. He spent parts of five other seasons in the major leagues, playing for the Kansas City/Oakland Athletics, Atlanta Braves, and Chicago Cubs.