After Effects built in motion blur is basically a short cut. To get things to blur (more) like they do in the real world, you need to use CC Force Motion Blur. CC Lens Blur imitates a defocus blur.
CC Force Motion Blur is also rather render heavy. For each iteration, it needs to render the layer another time. So, for a 1 hour render with 16 iteration force motion blur, you get 16 hours.
You could just apply it to the ball action layer (or whichever needs it) but you have to precompose first and then AE will add its own layer of motion blur, creating a double blur which is wrong.
Often these things don’t notice too badly,but when you’re using anything that has movement on it that is not created by AE’s standard transform properties this is always going to be an issue.
The correct way round it is CC Force Motion Blur on the whole scene.
What I usually do is explain to buyers in the user guide that there are two options. One gives you perfection at the expense of time, the other gives you speed at the expense of quality.