Bill Russell is an all-time defender, and he belongs in every conversation when discussing the greatest to ever do it. They should account for context, and that's where Bleacher Report's decision to put Russell ahead of Tim Duncan gets it wrong. Dominating in an eight-to-14 team league isn't the same as anchoring elite defenses for nearly two decades in a 30-team NBA. In his 19-year career, The Big Fundamental only allowed the Spurs to finish outside of the top-10 in defensive rating twice. San Antonio maintained a top-three defensive rating with him on the floor in each of his first 11 years in the league.