Southworth played more regularly in 1919, appearing in 121 games and leading the league with 14 triples. With the exception of two seasons, Southworth played in at least that many games through 1926. In 1926, Southworth's offensive production increased and he finished the season with a .320 batting average, 16 home runs and 99 RBI. He ran into difficulty with New York manager John McGraw that year, as Southworth's independent style became incompatible with McGraw's strict leadership. He was traded from the New York Giants to the St. Louis Cardinals in the middle of the season. Southworth suffered a 1927 rib injury that limited his playing time. The Cardinals' leadership began to look for a role for Southworth beyond his playing career.