Hager attended Sierra Vista High School in Spring Valley, Nevada, where he was a four-year starter on the baseball team.

[5] After signing, Hager made his professional debut that same year for rookie–level Princeton Rays and spent the whole season there,[6] batting .269 with four home runs and 17 RBI in 47 games.

On October 29, 2018, Hager re-signed with Milwaukee on a minor league contract that included an invitation to spring training.

[15] He made his MLB debut for the Mets that day against his former draft team the Tampa Bay Rays as a pinch hitter in the top of the 9th inning for Kevin Pillar, lining out to center field in his only at-bat.

On May 21, Hager recorded his first major league hit, a single off of Miami Marlins reliever Adam Cimber.

[19][20] Hager hit .214/.294/.469 with 6 home runs and 11 RBI in 26 games for the Triple-A Tacoma Rainiers before he was designated for assignment on July 27.

On May 16, 2022, Hager was selected to the active roster and started Game 1 of that day's doubleheader against the Los Angeles Dodgers.

[27] On October 2, Hager was re-selected to Arizona's 40-man and active rosters, but did not make another appearance for the team to finish out the season.

[28] On November 3, Hager was removed from the 40-man roster and sent outright to Triple–A; he subsequently elected free agency in lieu of the assignment.

[30] In an April 27 game in which Reno defeated the Sugar Land Space Cowboys 24–2, Hager recorded 5 hits in 5 at-bats with a home run and 8 RBI.