Brady and Maroney are coming off of injuries. Morris has been getting injured a lot over the past couple of years. Taylor just turned 948 years old (running back years) and Faulk is a 3rd down back as opposed to a starter.
I've got no problem with them being ranked "only" #4. If the players can reach the levels most of us expect, this group will quickly shoot up the charts to #1. I just can't see worrying about this when injury is clearly a part of the 'low' ranking. A healthy Brady and relatively healthy running backs corps would make the Patriots the clear #1 in this list, but it's not as if the author is the only person in the world taking a "show me" attitude.