In 2017, as a freshman at North Carolina, Busch appeared in 55 games, hitting .215 with three home runs and 22 RBIs.[5] After the season, he played in the Northwoods League for the St. Cloud Rox.[6] As a sophomore in 2018, Busch started all 64 of North Carolina's games, batting .317 with 13 home runs and 63 RBIs.[7] He batted .636 during the NCAA tournament's Chapel Hill Regional and was named the Most Outstanding Player,[8] helping lead North Carolina to the 2018 College World Series.[9] He was named to the All-ACC Second Team.[10] Following the season, he played in the Cape Cod Baseball League for the Chatham Anglers, where batted .322 with six home runs in 27 games and was named to the All-Cape League Team.[11][12] Prior to the 2019 season, Busch was named a preseason All-American by multiple media outlets, including Perfect Game and Baseball America.[13][14] Over 65 games, he batted .284 with 16 home runs and 57 RBIs.[4]
For the 2021 season, he was assigned to the Tulsa Drillers.[20] In June, Busch was selected to play in the All-Star Futures Game at Coors Field.[21] Busch appeared in 107 games for the Drillers, hitting .267 with twenty home runs and 67 RBIs, while primarily playing second base.[4] He was selected as a post-season Double-A Central All-Star.[22] He returned to Tulsa to begin the 2022 season.[23] After batting .306 with 11 home runs and 29 RBIs over 31 games he was promoted to the Oklahoma City Dodgers,[24] where he hit .266 in 111 games with 21 homers and 79 RBIs; he primarily played second base for the two teams.[25]
On November 15, 2022, the Dodgers added Busch to the 40-man roster to protect him from the Rule 5 draft.[26] He was optioned to Oklahoma City to begin the 2023 season.[27] He was called up to the majors for the first time on April 25 and made his debut as the designated hitter against the Pittsburgh Pirates.[28] He was selected as the organizations Minor League Player of the Year[29] after he hit .323 with 27 home runs and 90 RBI in 98 games for Oklahoma City,[4] helping them win the Pacific Coast League (PCL) championship.[30] In 2023 in Triple A he played primarily third base (61 games) and second base (26 games).[31] He was honored after the season as the MVP and Top Prospect of the PCL.[32]
In 2023 Busch played in 27 games in the majors, and hit .167/.247/.292 with two home runs and seven RBIs, with 27 strikeouts in 72 at bats. He played 13 games at third base, four at first base, one at second base, and eight at designated hitter.[33] His first major league hit was a single off of Johan Oviedo of the Pirates, and his first MLB home run was off Gavin Williams of the Cleveland Guardians on August 24.[34][35]
Chicago Cubs
On January 11, 2024, Busch and Yency Almonte were traded to the Chicago Cubs in exchange for Jackson Ferris and Zyhir Hope.[36][37] From April 10 to 15, Busch homered in five straight games, tying the longest streak by a Cub.[38] Over the season, he would spend most of his time at first base, only playing 18.1 innings at second and third base combined. Busch finished the season with 21 home runs and 65 RBI while slashing .248/.335/.440.[39]