Knocking back Nasus when he Has his Q charged and and already has a target he is running towards it if you Knock him back he will automatically Q which ever target he targeted. ive seen it with in a 500 range idk how far it is able to function at but. It removes one of the only counter play versus Nasus zoneing him early game and delaying his late game stacks.
When most auto attacks start there's not a whole lot that can stop them, particularly when it comes to melee auto attacks. Nasus's Q is an auto attack enhancer, so it follows all the rules of a regular auto.
Basically if he starts his Q attack the only thing that's going to stop him is death.
Knocking him back isn't really a good way to deny him stacks, however. The cooldown on his Q is just too low. It's better to focus on being a strong enough dueler that he physically cannot fight you. He either gets a few stacks and dies or he sits back and lets you freeze the lane.
If you're having trouble with him I suggest trying Darius, as he is relatively easy to shut Nasus down with.
