The worn teeth thing is worth emphasizing, my pup, at only 16 months, had a tooth repaired. The Vet's first comment to me afterward was "you let her play with tennis balls don't you". But only for about six months did I allow that! At any rate, he said her canine teeth showed obvious signs of wear. I had stopped playing with her with tennis balls some time before that, but for him to comment on that at her young age really made an impression on me! Don't let your your puppy or dog play with tennis balls! Rubber balls are the way to go!I have one that'll do as you describe and another that'll just carry around her ball and chomp on it as long as you let her. I limit "ball time" as she has worn her teeth from this doing this. She will substitute sticks and other random things too and carry them around.