We Panther fans obviously want to see Double Trouble tearing up the NFL for the next 50 years. However, it's generally accepted among us that eventually they'll have to cut one loose because they will want to be featured backs and we simply cannot pay them the money for that and for a while I agreed with the idea. However, after reading the football outsiders article that bmoyer put up, I started thinking that it would behoove DeAngelo Williams and Jonathan Stewart to continue sharing the Panthers backfield from both a career-extending and financial standpoint.
Football Outsiders claims that a running back's effectiveness starts to decline at around 28 years old and falls off dramatically if a season with 370 carries is achieved. Williams will actually turn 28 years old next April while Stewart is only 23 years old, so if ever a choice has to be made then it should probably be Stewart, who has also carried the ball 350 fewer times.
However, if they stay together, they would probably extend their effectiveness a few years. Assuming that the decline happens sometime around 1800 carries or about six seasons of 300 carries each. That number is somewhat random as it estimates the average years it takes a runner to get to 28 and how many carries a workhorse runner typically gets. Currently Williams is at 754 while Stewart is at 408. If they continue splitting carries like they did last year, that would put them both at about 225/year, making it four and a half years before Williams reaches 1800 and six years before Stewart does. And while that's where my hypothetical drop-off point is, there would also still obviously be a few more years of perhaps decreased effectiveness left. Also, with fewer carries it would be statistically and physically easier for the two of them to keep their near five yards per carry average that we love. Not only that but those few more years of potentially decreased effectiveness would be less painful for the two I'm sure.
So in so many words I basically described that our running back are extending their careers and would be if they continued like this. But we all knew that. The problem is more the money. We cannot afford to keep two of the best running backs in the league on our roster. However, say the two take a pay cut at first. We could pay the two of them combined a few million more than the highest-paid running back in the NFL at the time, say $7 mil a year a piece for four years. After those four years the highest-paid running back in the NFL would probably have severely declined while Double Trouble could still be going strong and could make another $5-6 mil a piece for another four years potentially.
Therefore it's a more sound long-term deal for Williams and Stewart to take the pay cut now and be effective longer and ultimately earn more money as well as being able to physically play for longer. Oh, and they'll help the Panthers win a few Super Bowls. That's pretty cool too.