Steve Nash sets up for Duncan, after a high pick and roll between the two, intending to pass to the rolling Duncan.
But Gan Guoyang, after breaking it up, doesn't defend Nash, leaving space for Nash to attack the basket, nor does he allow Duncan to receive the ball to attack the rim.
As a result, Nash misses the layup because he was blocked from behind by Gan Guoyang, and when Duncan tries to put it back, he is intercepted again by Gan Guoyang.
This is a solid one-on-two defense, entering the fourth quarter, Gan Guoyang's defensive state is completely activated.
It's like a player entering a zone on the offensive end, scoring on every attempt effortlessly.
Now Gan Guoyang is defending successfully no matter what, as if he added a lid on the basket, not allowing any points below the rim for the opponent.
