Very few players in the field are even remotely capable of doing what Dustin Johnson is doing to Shinnicock (i.e., the course requires such power and accuracy - i.e., a pure swing & striker of the ball - to record sub-par scores, Johnson probably wins this thing easy if he just plays par golf the rest of the way in...). If he keeps playing as well as he's playing off the tee (i.e., giving himself easy approach shots relative to the rest of the field and therefore having a much higher GIR), nobody is going to catch him and there's probably a better chance that he just "runs away & hides" from the rest of the field.