Arnovich's professional baseball career began at age 22 with the Superior Blues, the champions of the newly revived Northern League in . Playing as a shortstop that year, he hit .331 and had a slugging percentage of .495 with 17 steals. Throughout the season he hit 14 home runs, putting him fourth in the league. His .918 fielding percentage was best of any shortstop with 50 or more games that season and made the unofficial All-Star team listed by the "Spalding Guide". Returning to Superior in , Arnovich hit .374 to take the Northern League batting title, and his 21 home runs (three in one game) tied for fifth.