The 22nd round draft pick of the Chicago Cubs in 2017, Messinger was a four-year letter winner for head coach Craig McBride at Niwot High School. He hit .484 with eight doubles, four triples, four home runs and 21 RBIs in 19 games his senior year and was a two-time all-conference honoree his freshman and junior years while being named the Northern Conference Player of the Year after his senior campaign. He was an academic all-state his junior and senior years. Messinger began his collegiate career in 2018 at Kansas University, hitting .229 across 54 games with 7 doubles, 1 triple, and 1 home run.