Can the ground cause a fumble if the ball carrier is untouched?
If the ball carrier is untouched then he is not down when he hits the ground so it would be a fumble. The ground cannot cause a fumble if the ball carrier hits the ground due to contact from someone on the defense. If the ball carrier runs into his own player, falls down, and fumbles, then it is a fumble.
If the player is untouched, then the play is still completely live; the ball carrier can get up and run more. On mistake a lot of rookie receivers make is to assume they’re down when they dive for a catch. I can’t remember who, but somebody actually put the ball down last week, but for some reason the refs gave the ball back to his team. On the other hand, I’ve seen more experienced WRs make a diving catch, and then roll into the endzone when nobody touches them (usually because the CB is just out of college).
That would be Plaxico Burress - and it isn’t the first @#$% time that he has done it. He got lucky because the official ruled the play dead because he had “given up his body” or some such. Although I am a Steeler’s fan, I wasn’t sure that I agreed with the call. It seemed to me that he had placed the ball down and it was still live - officially a fumble.