3. Roger Bresnahan (1902-1908)
Wins Above Replacement: 27.2
Bresnahan played seven seasons with the Giants. The Hall of Fame catcher played 17 seasons in Major League baseball. His best season with the Giants was in 1908, with a WAR of 5.9. For six seasons, from 1903-1908, He had at least a 3.5 Win season.
Overall, he played 751 career games at catcher in New York and had a career slashline with the Giants of .293/.403/.393 for an OPS of .795.