Setting aside aspirations of being a star pitcher, McCarthy finally settled into an everyday position in a lineup in with the St. Louis Browns in the American Association. With the Browns until , McCarthy scored over 100 runs each season and grew increasingly productive at the plate. He batted .350 in and drove in 95 runs in 1891. Although the shoddy record-keeping of the time prevents an accurate tally, he also asserted himself as a daring presence on the base-paths, by some accounts stealing over 100 bases in 1888 and approaching the mark in 1890.