It's no secret that Kawhi Leonard's impact goes beyond the box score, but even advanced stats (which have him tops in the league in Defensive Win Shares) can't quite qualify what makes Leonard such a transcendent two-way player.
With averages of two steals and almost a block a game, great footwork and the length to contest almost any shot, his on-ball defense alone makes him worthy of the praise that he's received both this season and last. Opponents shoot almost 8% worse from the field when guarded by him, and his rim defense is on par with the league's best big men. Yet it's the reigning DPOY's alertness and activity as a secondary defender that elevates San Antonio's NBA-best defense.
Playing within the Spurs system
Help defense is generally a big man's game. Their length and positioning on the floor facilitate their ability to crash the party and draw charges or contest shots around the rim. It's part of the reason that power forwards and centers have been traditionally valued more for their defense; even great lockdown wings like Paul George and Jimmy Butler are still limited in what they can do compared to a seven-footer that patrols the paint and stifles pick and rolls. Kawhi Leonard is an exception.
Part of this begins with the Spurs' defensive philosophy on the whole. Rarely do players sleep on a play; what you almost always see is ten eyeballs that are minding the ball and their man, bodies rotating in unison and switching when necessary. Perimeter defenders fight through screens, while bigs switch and take away angles to the basket. It is an ecosystem designed to prevent plays from developing, and guys aren't afraid to overplay once they have cut off the first option.
While mindfulness and effort are key, not all defenders are created equal, and Kawhi has the physical tools to commit and make a play on the ball from anywhere on the floor. Dribble near him and he's prepared to stick a mitt in there and get the steal. Forget about him on the pick and roll and he'll casually blow it up and take the ball the other way.
For some defenders this is strictly 'freelancing', but Leonard takes on the responsibility without getting burned by his guy all that often. Sometimes all it requires is him taking a step in, as big men often do, to dissuade a playmaker. It's a subtle gesture that is probably more effective due to his reputation. But it works.
On the far baseline
Leonard on the weak-side baseline might be where he's most interesting.
With full visibility of the floor, he becomes an NFL safety, a ball hawk ready to make the play. He's constantly toeing the painted area, respecting the 2.9-second hot lava while waiting for the play to unfold.
A few possessions before this one, Chandler was able to rise for the easy alley-oop. Leonard anticipates it this time, making an athletic play in the air that few can duplicate.
Helping on mismatches
The Spurs switch often, which can be risky when they involve little dudes like Tony Parker or Patty Mills on a forward or center. These situations are mitigated when you have Leonard on the wing and a defensive unit that's prepared to rotate accordingly.
On two occasions the Hawks got the matchup they wanted down low, and both times Leonard was there to thwart any look at the basket, again reacting as we're most often used to big men doing. If you need tips on how to scare off a bear in the wild, you can do worse than following Whi's example.
And again here, against the Hawks.
The Spurs defense benefits from cohesion, communication and elite defenders at various positions. But it helps to have a unique talent that can shut down the league's best perimeter players and step in to make plays. This is elite level big man rim-protection here ... from a small foward.
The fact that Kawhi can take on primary defensive assignments and be this active as a help defender, while only commiting two fouls per game, is astonishing. That he can then turn around and be one of the most efficient offensive players of the game is the reason why he's getting serious consideration as an MVP candidate.