[7] The St. Louis Cardinals selected Nootbaar in the eighth round of the 2018 Major League Baseball draft.

[12] Nootbaar began the 2021 season at the Cardinals' alternate training site before being reassigned to the Triple-A East Memphis Redbirds.

[18] He hit his first career home run as a pinch-hitter off JT Brubaker in a 7–6 win over the Pittsburgh Pirates on August 12.

[20] On August 25, Nootbaar got his first career walk-off hit, a single in the 10th inning against Tigers relief pitcher Michael Fulmer.

[23] Nootbaar entered the 2022 season as the Cardinals' fourth outfielder before eventually moving into a starting role after injuries and positive play.

[25] In 2006, a Japan national youth team toured the US, including future MLB player Masahiro Tanaka and Japanese high school pitching phenom Yuki Saito.

[26] Nootbaar served as a batboy and interacted with the team, including stretching and playing catch, and some of the players stayed at his house and shared meals with the family.

[26] According to his mother, this experience was later influential to Nootbaar accepting an offer to join the Japan national team for the 2023 World Baseball Classic.

[16] Nootbaar's older brother, Nigel, was a pitcher at USC and played professionally in the Baltimore Orioles system.