Mueller was one of Cardinals manager Branch Rickey's favorite players, though his baserunning exploits turned all his managers gray. He missed half of 1925 because of a broken foot, and in 1926 he was traded to the Giants. There he told manager John McGraw he wasn't used to being chewed out, and was soon dealt to the Braves. Entering both games of a 1927 doubleheader as a pinch hitter, Mueller drove in eight runs in three at-bats. His brother Walter was an extra outfielder with the Pirates in the 1920s, and his nephew, Don, played 10 years for the Giants.