Danny had a retained testicle, though the one was fine. We had him neutered because I'd heard that the retained one can cause problems later in life, though I don't know how true this is. We were never going to breed from him anyway, and I would have hated to pass the condition on. Our vet did say though that at nine months the testice could still drop, so if you can feel it perhaps it will (Dan's was right up inside his tum and couldn't be felt, it took the vet a while to find it when they opened him up).