[3] He was not drafted out of high school and attended Niagara University in Lewiston, New York to play college baseball for the Purple Eagles.
[12] On September 2, Brash threw six perfect innings to start a combined no-hitter, finished by relievers Nate Fisher and Dayeison Arias.
[15][5] On September 28, Seattle selected Brash's contract to the 40-man roster and promoted him to the major leagues for the first time, although he did not make an appearance.
[18] He made his MLB debut on April 12, striking out six in 5+1⁄3 innings but allowing the only run in a 1–0 loss to the Chicago White Sox.
In the minors, Brash converted to a reliever and lowered his walk rate moderately, pitching in 26 games and earning 3 saves.
[5] The Mariners recalled him on July 9 and he became a setup man for the team, earning 9 holds and a 3–1 record in the final three months of the season.
Brash was the winning pitcher on September when the Mariners clinched their first postseason appearance since 2001, throwing a scoreless inning against the Oakland Athletics[21] before Cal Raleigh's pinch-hit game-winning home run.