On pass plays when the LB is assigned to "spy" the QB he just stands there instead . Until, that is looked at I don't expect QB to average much more 10 yards a game . Faster is better and a QB could break one but they are far and few in between .
If QB running was opened back up even slower ones would average 5+ a carry. Fast ones had numbers 10+ and 1000 yard seasons . Granted this was a lot of seasons ago.
Still in general the scrambling rating should moderate this effect. A low rating is not bad but perhaps that QB is considered a pocket passer. Scrambling dictates how often a QB will reset his feet. In theory he would have more opportunities to run but after he checks if there are open receivers again .
Still, I would rather have it opened back up and just don't pick spy plays until it's fixed. So many easy plays that turn in to sacks or passes back across the feild.
