My first thought, birds of prey could get him for an easy meal, it isn't uncommon. Someone could steal him. He could eat something bad out there and get very sick. Other dogs or cats could get into your yard and anything could happen to a puppy all alone in that situation. Puppies are like babies in where they need special protection, especially while they are growing, as many they taste/eat everything to explore their world.
Keep up with the crate training.
Keep up with the crate training.
