Tom Jager is a rookie for the 2021 Windy CIty ThunderBolts. He signed as a free agent on June 11, 2021. Jager graduated from Roosevelt University, for whom he played his home games at Ozinga Field. As a senior, he went 6-3 with a 3.13 ERA. He struck out a school-record 77 and walked only 14 over 69 innings and was named First Team All-Chicagoland Collegiate Athletc Conference.

Jager started his collegiate career at Robert Morris University and played there for four years before the merger of Robert Morris and Roosevelt. Overall, he went 11-10 with five saves and a 4.47 ERA in 51 games (11 starts). In his best season, as a junior, he won six games, saved three and had a 2.84 ERA. He attended Oak Forest High School in Oak Forest, IL.