It's no secret that with Chase Holbrook in there, the Aggie running attack is more successful.
NMSU couldn't run with J.J. McDermott in at QB. I mean, they ran, but not well. Teams would stack the box on the Aggies and force them to throw it.
Chase changes the dynamics of the offense because the opposition needs to respect the pass. Idaho's defense is probably not as good as Boise's or La Tech's, but still, the team ran it much better and Holbrook's presence had a lot to do with it.
Heck, the entire offense played much better with him in there. An injury at QB, for most teams, is almost impossible to make up for.