One of the very best ways to catch fast action, especially if you lack the fast expensive auto focus lenses is to pre focus. Rather than trying to chase the action with a lens that cant keep up, try this.
It's all timing but it's really easy and very effctive.
you can anticipate the dogs movements, especially when they are returning to their trainier. You pick an area where you know the dog is going to be, maybe a second or two in from of him/her, focus on it, and when the dog gets to that area, you take the shot.
With the kind of light you had in that shot, you could even stop down a ways to give yourself a bit more dof. . .