Ketterer joined the Timbers on loan for the 2021 season.
The Madison, Wisconsin, native played the previous three seasons for El Paso Locomotive FC (2019-21), notching 22 shutouts in 55 appearances (55 starts) across all competitions.
During the 2019 USL Championship campaign, Ketterer played in 32 games and logged 12 shutouts, helping El Paso qualify for the playoffs in its inaugural season.
During the 2020 campaign, Ketterer posted nine shutouts in 16 appearances.
Originally drafted by Columbus Crew SC in the fourth round (71st overall) of the 2017 MLS SuperDraft, Ketterer made one appearance across two seasons in Columbus (2017-18), starting and playing 120 minutes in the fourth round of the 2018 Lamar Hunt U.S. Open Cup against the Chicago Fire on June 6, 2018.