It is never safe to be a ref and trying to keep ypur eyes peeled for incoming collisions from every direction.
One ref founf that out the hard way during the Texas Longhorns game against Kansas State.
A Kansas State player was in the midts of finishing a block on an opposing player when his momentum got used against him and went straight into the turf. He would hit a ref in the legs and that guy would guy face first into the turf.