i tried to do the same thing with my dog, so i can appreciate the difficulty in capturing the "stopped motion" in this. the dog's eyes and his mouth are so wide opened, it really reflects well the thrill of playing the ball. well done.
I have a boxer that looks a lot like this guy. Aren't they great? Good stopped motion (I know how fast the move) but the composition is just not very pleasing.
This is a good shot.. the whites of the eyes give a kind of crazy look. I would probably try to crop the body out and have a close up of the face (if megapixels allow), or failing that get a closer face shot. The reason for that is that I don't think the body is adding much to the image. For me, it's all in the face.