Busenitz began the 2017 season with Rochester, and pitched to a 1.25 earned run average in his first 29+1⁄3innings pitched of the season. On June 17, 2017, he was selected to the 40-man roster and promoted to the major leagues for the first time.[7] He made his MLB debut that day, pitching 2.0 innings of 1-run ball against the Cleveland Indians. He finished his rookie season with a neat 1.99 ERA in 31.2 innings pitched across 28 contests. In 2018, Busenitz could not replicate his success from the previous year, struggling to a 4–1 record and 7.82 ERA in 23 major league appearances. He was granted his unconditional release on November 20, 2018, so he could sign with a team in Nippon Professional Baseball.
Tohoku Rakuten Golden Eagles
On November 20, 2018, Busenitz signed with the Tohoku Rakuten Golden Eagles of Japan's Nippon Professional Baseball (NPB).[8] In his first NPB season, Busenitz logged a 4–3 record and stellar 1.94 ERA in 54 appearances for Rakuten. On December 3, 2019, Busenitz signed a 1-year extension to remain with the Eagles.[9] By 2022, Busenitz had pitched in 165 games for the Eagles, recording a 9–8 record and 2.83 ERA in 155+2⁄3 innings pitched.
Cincinnati Reds
On December 27, 2022, Busenitz signed a minor league contract with an invitation to spring training with the Cincinnati Reds.[10] He was assigned to the Triple-A Louisville Bats to begin the 2023 season, where he recorded a 1.80 ERA with 13 strikeouts and 3 saves across 15 appearances. On May 14, 2023, Busenitz's contract was selected to the active roster.[11] In 5 games for Cincinnati, he registered a 3.60 ERA with 3 strikeouts in 5 innings of work. On September 1, Busenitz was designated for assignment.[12] He cleared waivers and was sent outright to Triple–A Louisville on September 4.[13] On October 1, the Reds selected Busenitz back to the major league roster.[14] He struck out two in two perfect innings against the St. Louis Cardinals in Cincinnati's final game of the year.[15] On October 9, Busenitz was removed from the 40–man roster and sent outright to Triple–A Louisville.[16] He elected free agency on October 12.[17]
On January 3, 2024, Busenitz re–signed with the Reds organization on a minor league contract.[18] In 40 games for Louisville, he compiled a 5–2 record and 3.93 ERA with 51 strikeouts over 55 innings pitched. On August 23, the Reds selected Busenitz's contract, adding him to their active roster.[19] He allowed 4 runs (3 earned) in one inning pitched and was designated for assignment the following day.[20] Busenitz cleared waivers and was sent outright to Louisville on August 29.[21] On September 20, Busenitz was added back to the major league roster.[22] After two more outings, he was designated for assignment on September 22.[23] Busenitz cleared waivers and was sent outright to Louisville on September 24.[24] On October 28, Buesnitz re-signed with the Reds on a minor league contract for the 2025 season.[25]
