He also played in the USL Premier Development League for St. Louis Lions, where he was a prolific goalscorer, netting 35 times in 36 games over three seasons with the team.

Heinemann was signed to his first professional contract by the Charleston Battery after impressing head coach Michael Anhaeuser during a pre-season trial.

[13] The club won the post-season playoffs for the league but folded shortly after due to financial difficulties.The finals match saw Heinemann score the winning goal on a penalty kick in the 19th minute as the Delta's claimed the 2017 Soccer Bowl.

[18] In February 2022, Heinemann was named head coach for the United States boys' national under-15 soccer team.

[19] Under Heinemann's stewardship the team won 6 consecutive matches, while outscoring their opponents 26–5, to claim the 2023 CONCACAF Boys' Under-15 Championship Final.

[20] In January 2025, Heinemann joined the staff of Major League Soccer side Chicago Fire as an assistant coach.