#3 Gabby Hartnett - New York Giants
Hall of Fame catcher Gabby Hartnett spent 19 seasons in a Cubs uniform from 1922-1940. He slugged 231 home runs and slashed .297/.370.490 while winning the 1935 National League MVP and earning six All-Star nods. Hartnett's shining moment was his "Homer in the Gloamin'" against the Pirates on September 28, 1938.
Like Cavarretta, Hartnett would be named a player/manager in his later seasons. After a losing season in 1940 (75-79) and only 37 games played, Hartnett was dismissed. That December he signed a contract with the New York Giants.
The 40-year-old Hartnett played in 64 games with the Giants in 1941, hitting .300/.356/.433 with five home runs. He played alongside Hall of Famer Mel Ott, but the Giants finished 25.5 games behind the pennant-winning Brooklyn Dodgers. Despite playing well as a backup catcher, Hartnett was released in September. He would then retire.
Roughly 97% of Hartnett's games played were in a Cubs uniform, with 3% being in a Giants uniform.