I know it was not my dog but would he have saved me if the other dog chewed them off?

It was the first day of dog walking. I walked this dark brown male staffy cross pitbull lurcher who is 3 years old. I walked him in the woods and this dog with no lead or coller smashed into me knocking me flying. He bit me all over before biting me in the groin and not letting go. It was all very very painfull but once he bit me in the groin and would not let go i was screaming and crying in agony. I felt a testicle between his teeth and the bite was getting harder slowly crushing a testicle. The dog i was walking was just standing there watching. The dog let go in the end but if my testicle had ruptured i would be absolutely screaming and crying in utter agony. Would the dog save me or still just stand there?