The following platoons say hello:
Adrian Peterson, Chester Taylor #1 Team RYPG
Fred Taylor, Maurice Drew Jones #3 Team RYPG
Lendale White, Chris Brown # 4 Team RYPG
Having 2 good backs allows you to keep both of them fresh.
And it allows your team to pile up the yards on the ground and control the clock.
If the Pats could control the game by running the clock out with the backs they have, don't you think they would have done so?
Maroney has certain limitations.
He hasn't proven to be a good short yardage back, goal line back, pass catching back, or 3rd down back.
And if you put Faulk in there you pretty much communicate to the defense that you're going to pass.
Adding a back who can do it all, like McFadden would make the Pats offense that much stronger, and tougher to predict and stop.
I'm glad you bring up the expiring contract point. If you have two very good backs then you don't HAVE to pay the market price for the back whose contract is expiring, that would be Maroney, you have that much more leverage in contract negotiations because you have an Ace in the hole.
YOu don't want to have a "platoon" of RBs one of whom makes 8M per year guaranteed largely and another 1st round pick.
And if they "last 8 years", great, you have to pay them more when their rookie contract is up.