Does your dog respond to treats? You’re going to use a lot of treats here, so you might want to cut them up small. Get him going in a large room with treats. Then take him out of the room, introduce a ball at one end, and re-enter. Move a few steps closer. More treats and every time his attention goes toward the ball, distract him with treats, and so on. Proceed like this until you are near the ball. If doggie balks, move back a step or two and begin again. It seems to me that you want to work with one type of ball, maybe a tennis ball, rather than a basket ball, which is large. Don’t move the ball until he gets used to it being still. After he’s OK with getting treats right close to the ball, you could begin again by having someone roll a ball across the other end of the room, and keep him distracted with the treats. Then do as before, moving a step closer to the rolling ball each time. I’ve seen this sort of thing done on “It’s Me or the Dog.