Barring injury or exceptional circumstances, a team's ace typically starts on Opening Day.
In addition, aces are usually preferred to start crucial playoff games, sometimes on three days' rest.
[1] The term may be a derivation of the nickname of Asa Brainard (real first name: "Asahel"), a 19th-century star pitcher, who was sometimes referred to as "Ace".
[2][3] In the early days of baseball, the term ace was used to refer to a run.
[5] For example, the April 27, 1981, Sports Illustrated cover was captioned "The Amazing A's and Their Five Aces" to describe the starting rotation of the 1981 Oakland Athletics.