The problem is not that Steve fumbled the ball (that's the outcome).  The problem is he's carring it in the wrong hand (the cause).  You're driving me nuts.................When running to the left, please carry the ball your left hand, and in your right hand only when you're running to your right!   

And coach, it's OK to remind Steve to carry the ball in the correct hand.  Even better, demonstrate what that would look like....ask him to confirm that he understands, then have him show you.  The next time he does it in a game, pull him out...talk to him, then give him another try.  Repeat as necessary until he never carries the ball in the wrong hand again.  It could save you a turnover in a critical game down the road. 

GO TEXANS!