At the end of the 1907 season, after a good showing in South Bend, Bush was drafted by the Chicago White Sox, Boston Red Sox and Detroit Tigers, and was awarded to the Tigers. He was sold by the Detroit team to play the 1908 season for the Indianapolis Browns of the American Association. He appeared in 153 games for Indianapolis and was the team's starting shortstop with 330 putouts, 472 assists, 54 errors, 856 total chances, and a .937 fielding percentage. As a batter, he had 28 stolen bases, 18 sacrifice hits, seven triples, and a .247 batting average. He helped Indianapolis win the American Association pennant for 1908, and at the end of the 1908 season, "The Sporting Life" wrote that Bush was "generally credited with being the best ball player outside the big leagues during the season in the minors which has just closed.