Zhangsun Shan and the Tang sect guy stood still facing each other in silence for quite some time. For some reason, the fight began with a test of patience. The one who loses their focus and advances to attack loses the advantage to his opponent.
I know for a fact that Zhangsun Shan had nerves of steel. He should have the ability to perceive the right timing to attack in duels like this, because I distinctly remember having to wait for the attack meter to fill up before making a move. Or else the fight would be highly disadvantageous.