It's not just that.
If there's a body (say, Bruschi) floating around in his possible scramble lane, Young won't run there.
Hobbs wouldn't work as a spy, unless he breaks off his WR every play and goes essentially into a midfield zone.
If he's on an flat zone, sure, but there's still the other flat to cover.
The only two guys on the field who are naturally in the best position to spy are the ILBs. They prevent the scramble up the middle, and can force the run to the sidelines if it goes outside.
The whole idea of a spy is for someone to physically be there to discourage the scramble, not for someone to actually run down the QB. It's more bark than bite.
Thanks for the great play analysis with Vick !! That is so interesting to see the breakdown and analysis.
I'll certainly defer to your judgment, but for myself I just can't quite see that somebody 'in a lane' discourages somebody like Vick - or perhaps Young. If he has any room to maneuver, I really don't think he's going to worry about somebody just being there. And, referee or not, I wouldn't give Davis much of a chance to stop Vick with Vick in the open field against him. That's why I have my personal doubts that a linebacker can do the job.
Blitzfritz - good thought on Colvin - he might be the one linebacker that, to me, might be able to do the job.
PATNUTSme - yeah, Scott is interesting.
Pats1 - one thing that was very interesting in the great example you gave was Sanders down there. Sanders might also be fast enough. Did he maybe let himself get tied up instead of staying loose to follow Vick ?
As I say, thanks for the play analysis, Pats1. That took some time to put together with the video clips and is much appreciated.
Don't know if this would fit in with what you said, but perhaps all the Patriots need to do is be extra careful to maintain their normal 3-4 discipline to slow Vick down and extra emphasis on pursuit.