Defensive Rating is confusing to me. I see several different sites who have Rudy #1 but Basketball Reference had Rudy #3 at 99.2 behind Draymond at 99.1 and Drummond at 99.0 when I looked this morning. I don't know how these sites come to different numbers.
Different sites calculate the number of possessions in a game differently. There's a simplified formula meant to estimate it (FGA + FTA*0.44 + TOs - ORebs), and then other complex formulas meant to get the exact amount.