It's not that he can't, it's that he's not doing it right now. What's interesting is that EG's greatest physical skills are getting him in trouble right now b/c they're being abused.
He's elusive as hell in the backfield so he tends to hold the ball longer than he should, gets too creative and takes the wrong escape path. He needs to be more decisive with the ball, take yardage that's given to him by land or air and understand that some plays just need to die.
His hands are giant vice grips so he tends to carry the ball recklessly. IMO, he's used to being on a field of defenders that were never able to take the ball away from him. He needs to figure it out real quick - these are division one athletes trying to tackle you and they will get that ball. This isn't uncommon for young college running backs. EG isn't young anymore and he needs to learn.
He's got a canon for an arm and he's extremely confident as a passer so he tends to throw into tight windows and push the ball deep. I'm fine with him throwing into tight windows at times b/c, let's face it, he can. Just manage the game and don't do it in critical moments, i.e., Stanford in the red zone. What's a bigger issue is his unwillingness, at times, to take the short or intermediate routes. He needs to take what the defense gives him, get into a 2nd or 3rd and short instead of a 2nd or 3rd and ten. It would open up the offense and prevent turnovers.
You do not sit a kid this talented. It would be a giant failure by the staff if they gave up on him and benched him. You play him, coach him and guide him.