Boston has the NBA’s best defense, though which player should get sufficient credit to be recognized as the best defender in the league this year? Six of the Celtics’ top seven (Smart, Williams, White, Jaylen Brown, Jayson Tatum and Al Horford) players rate in the 84th percentile or higher in dEPM. Smart’s candidacy is hurt by the fact that it’s been so long since a guard won the award that I’m not sure we would recognize what DPOY-level guard play even looked like. As Smart himself put it, those are the rules…