Kawhi was barely matched up against KD on EITHER end, Pop assigned Kawhi to check Russ & put Danny Green on KD. The only time Kawhi checked KD was once he got hot & it's impossible to slow him down when he's going nuclear.

On the other end, KD was hiding on Danny & occasionally checked Kawhi. Basically, KD didn't expend anywhere near the amount of energy Kawhi did on the defensive end. Russy's assignment was Tony, who ended up having flashback games throughout the series.

Even then, let's see how he fared:

-WestBrick: 25/6/10/2 (27 TOs / FG: 37% / TS: 47%)
-Kawhi: 23/7/3/2 (12 TOs / FG: 48% / TS: 55%)**Was primarily being guarded by Roberson who is a very good defender, actually that's his only asset**

http://www.basketball-reference.com/playoffs/2016-nba-western-conference-semifinals-thunder-vs-spurs.html

Gm 1 (Utter domination): https://www.youtube.com/watch?v=iq8TIWVdqpE

Gm 2: Russ didn't score a single basket against Kawhi when OKC stole HCA but let's blame Kawhi's 7/18 night when Patty is air-balling a WIDE OPEN 3: https://www.youtube.com/watch?v=lV9LRdSLHeQ

-Russ averaged 22 drive per 100 possession in the regular season & 1st rd but against Kawhi he averaged 2 drives per 100 possession in the first 2 games: (http://espn.go.com/video/clip?id=15472072)

Gm 3 (Kawhi steals back HCA): https://www.youtube.com/watch?v=bl-EiA_0Z_4

Gm 4 (KD goes nuclear): https://www.youtube.com/watch?v=ri0K5J1NtoI

Gm 5 (KD is MIA in the 4th but nobody talks about it b/c OKC won thanks to the refs & Tony missing 2 wide open jumpers along w/ a critical FT): https://www.youtube.com/watch?v=USrTrtM4t1o

Gm 6 (The game got out of hand when Pop subbed in Kyle Anderson for Kawhi late in the 1st quarter while the Spurs were up 2: "2:47 K. Anderson enters the game for K. Leonard 19-17"): https://www.youtube.com/watch?v=cbvpUWXQ_iA

Name me another player that had to check a high usage player like Russ for 40 minutes & dropped an efficient 23 essentially playing ISO ball against a solid defender like Roberson?

Let's see how Kirby fared when he had the Kawhi assignment:

2001 Finals:
-Kirby (2nd option & DIDN'T have to guard AI 48 minutes): 24/7/5/1 (18 TOs / FG: 41% / TS: 50%)
-AI aka Original WestBrick (didn't have KD / played 1 on 5): 35/5/3/2 (12 TOs / FG: 40% / TS: 48%)
-https://www.youtube.com/watch?v=Yob7Ov9-wW0

2004 Finals:
-Kirby (Wanna be 1st option): 22/2/4/1 (18 TOs / FG: 38% / TS: 45%)
-Rip: 21/5/4 (23 TOs / FG: 40% / TS: 50%)
-https://www.youtube.com/watch?v=nhN41MWk8EA

2008 Finals: (**Closest scenario to the OKC series since Kirby HAD to primarily guard Pierce & at times Ray since Ariza was injured**)
-MVP Kirby (Pau=LMA): 25/4/5/2 (23 TOs / FG: 40% / TS: 50%)
-Pierce: 21/4/6/1 (22 TOs / FG: 43% / TS: 58%)
-https://www.youtube.com/watch?v=JkXnQba6Phg

-Bron at 24 won 66 games & lost to none other than Dwight in the ECF while dogging the closeout game: https://www.youtube.com/watch?v=71yVR0PyctM

-Pippen in his prime got outplayed by Penny & lost in the 2nd rd to the Magic even w/ Jorn on his squad.

BTW, remember 24 year old KD's 2013 2nd rd series against the same Tony Allen that Kawhi wrecked in the 1st rd:

"OKLAHOMA CITY — During the fourth quarter, Kevin Durant could often be found leaning over, grabbing his shorts. Yeah, the Oklahoma City Thunder's superstar was gassed — but the universally recognizable sign was unnecessary. Going into the final seconds, the stat sheet told the story: 5-for-20.

Even so, down two points in the final seconds Wednesday, there was never a question, who would take the last shot for Oklahoma City. On this night, given Durant's evident fatigue, maybe the outcome wasn't surprising, either.

After going 2-for-13 and scoring only five points beginning with the fourth quarter of Game 4, Durant's slump worsened. At times, he seemed frustrated — though he later denied it — by the combination of Memphis' defense and a shotmaker's sudden inability to make shots.
"I gave it all I had for my team," Durant said. "I left it all on the floor. I missed 16 shots, but I kept fighting and I kept being aggressive. That's all I can ask for."

But as his shots fell short, he passed up seeming opportunities. For long stretches Wednesday, the Thunder's best player disappeared. Durant's first attempt of the second half — another miss — came almost five minutes in, with Memphis up by 14. A moment later, Durant rebounded his own free throw miss and scored. Next trip downcourt, with a rare open transition 3-pointer, he threw up an air ball."