He worked as a Certified Public Accountant at a firm for five years, before joining the front office of the Minnesota Twins, starting as their director of finance in 1989, and receiving a promotion to vice president in 1992.
[1][2] Mather joined the Seattle Mariners organization in 1996, serving as executive vice president of finance and administration.
[1] In July 2018, a Seattle Times article reported that Mather contributed to creating a hostile workplace environment for women.
Mather spoke at a Bellevue Breakfast Rotary Club event in February 2021 in which he confessed to manipulating the service time of Mariners prospects during the 2020 season.
He made comments about the poor English-language skills of some of the team's foreign players, specifically complaining about needing to hire interpreters for players, such as Japanese pitcher Hisashi Iwakuma and remarking on the poor English of Julio Rodríguez, a Dominican prospect.