Rating an NBA player's defense is a tough call. Steals and blocks come into play, but they don't tell nearly the whole story. If Defensive Disruption could be rated numerically, Marcus Smart would be on the All-Defensive team every season.
Same deal with muscling-the-ball-our-of-opponents-hands. I have no recollection of another player doing this as often as Marcus. Face-to-face he just takes the ball away. Smart also has another maneuver where he puts his arm through the small space created by the opponent's crooked arm and body to get his hand on the ball.