Last season, the Jets were beaten time and time again by speed running backs on the outside. It was abundantly clear week 3, when the Jets played the Oakland Raiders. Take a look at some tape from that game:
McFadden, play after play, beat the Jets on the outside. He would make one move, and the Jets were pinned inside, leaving McFadden free reign to roam for yards on end. This was a problem time and time again for the Jets run defense in 2011. The defense was typically tough between the tackles, but one move to the outside and there was nobody there.
The speed will help, as obviously being fast helps in running down quick backs. But if nobody is on the outside, they will be carved up again by opposing backs.
Then what will make the difference?