Ketterer was a three-sport athlete in high school, playing basketball and tennis before turning his focus solely to soccer.

He was selected by Columbus Crew SC in the fourth round of the 2017 MLS SuperDraft and made his professional debut in the 2018 U.S. Open Cup.

Ketterer entered the 2014 season, his sophomore year, as the second-string goalkeeper, but took over the starting job after an injury to starter Shay Niemeyer.

[8] Ketterer was named a Second Team NSCAA Scholar All-North/Central Region[9] and earned a place on the MVC Honor Roll for the second consecutive season.

Although Stuver departed the club ahead of the 2018 season, Ketterer remained as the third-string goalkeeper for Columbus after Jon Kempin was acquired in a trade from LA Galaxy.

With Steffen off on international duty, Ketterer was handed his professional debut on June 6, 2018: he got the nod for a fourth round U.S. Open Cup fixture against Chicago Fire.

[21] On January 18, 2019, Ketterer joined USL Championship team El Paso Locomotive FC ahead of their inaugural season.

[23] On May 13, 2021, Ketterer joined MLS side Portland Timbers on loan for the remainder of the season following a season-ending injury to their goalkeeper Jeff Attinella.

[26] Ketterer made his debut for CF Montréal with a clean sheet on April 18, 2023, in a 2–0 home win against Vaughan Azzurri in a Canadian Championship match.