Keller played high school soccer at The Principia in St. Louis, Missouri, where he was named First-team All-State selection, helping to lead them to a state championship his freshman year.
Keller also played club soccer with the Saint Louis FC academy, where he helped the U-19 side advance to the USSDA playoffs in 2018.
He signed an academy contract with Saint Louis FC in 2019, making a single appearance for the club in the US Open Cup on May 29, 2019, against Forward Madison.
Keller was part of the USL League Two roster for St. Louis Scott Gallagher during their 2021 season, but didn't appear for the club.
[5] In January 2022, it was announced that Keller had signed a Generation Adidas contract with Major League Soccer, and would leave college a year early to enter the 2022 MLS SuperDraft.