Introducing RB Score

Posted on January 15, 2007 by


Growing up my favorite football players were the running backs. Earl Campbell, Tony Dorsett, and Walter Payton topped the list for me in the mid-1970s. And then – as a Lions fan — Billy Sims in the early 1980s and Barry Sanders in the latter part of that decade became my favorites.

We all know that Sanders was the greatest running back, both on this planet, in this universe, and in at least five parallel universes from which we have collected data.

Who, though, is the “best” running back today?

To evaluate quarterbacks we have proposed QB Score, which is calculated as follows:

QB Score = All Yards – 3*All Plays – 50*All Turnovers

Perhaps we can modify this simple formula to measure the contribution of running backs. Running backs both run with the ball and catch passes. These players also tend to fumble. Given what we know about the value of yards, plays, and turnovers, the performance of a running back can be evaluated as follows:

RB Score = All Yards – 3*All Plays – 50*Fumbles Lost

All Yards includes yards gained from rushing and catching passes. All Plays includes rushing attempts and receptions. And Fumbles Lost is how running backs lose the ball (except for the occasional errant half-back pass). reports data on all these statistics back to 1994 (I can’t find fumble lost before 1994). With RB Score in hand, I evaluated all running backs from 1994 to 2006. The top 40 in RB Score are listed HERE.

When we think of top running backs we typically focus on yards rushing. Backs, though, gain yards via the passing game as well. Plus, it’s important to note that fumbles lost also impact outcomes. When we consider more of what a running back does on the field (we don’t have everything since we are not considering such things as blocking or dropped passes), our list of top running backs differs from what we see when we just look at rushing yards.

Since 1994 the best rushing performances was posted by Jamal Lewis, who gained 2,066 yards on the ground in 2003. He also lost six fumbles that season – a mark that tops all of the Top 40 running backs listed – and only gained 205 yards receiving. So his overall productivity – measured via RB Score – only ranks 32nd.

Lewis posted a RB Score of 732 in 2003. This is good, but a bit short of the 1,ooo mark that appears to separate the very good from the truly outstanding. Since 1994 only six running backs have posted an RB Score above 1,000. Tiki Barber (in 2005), Priest Holmes (in 2002), and Charlie Garner (in 2002) each did this once. Marshall Faulk turned the trick twice (in 1999 and 2000). Barry Sanders also did this twice, in 1994 and 1997. Finally, LaDainian Tomlinson has done this twice. The first time was in 2003 and the second time was this past season. So according to RB Score, Tomlinson was the best back in 2006 (which is not a surprise).

A mark of 1,000 is relatively rare. As one can see in the top 40 list, a mark close to 700 is still quite good. In 2006, six backs not named LaDainian came close to 700 or moved well past this benchmark. These six backs include Steven Jackson, Tiki Barber, Brian Westbrook, Frank Gore, Larry Johnson, and Maurice Jones-Drew.

The overall RB Score is interesting, but one might also wonder who gives you the most per times touching the ball. If we look at RB Score per Play, which one can see HERE, the top 40 looks a bit different. Since 1994 only four running backs have had a per play mark above three. These include Faulk – who did this twice – as well as Sanders, Garner, and from 2006, Jones-Drew.

Does this mean that Jones-Drew was the best back in 2006? For running backs there is value in durability as well as efficiency. Jones-Drew has yet to show that he can be productive getting 300+ carries in a season. Hence overall RB Score might be more indicative of value.

The Top 40 lists tell us about the best of the best in the last 13 seasons. What about the 2006 collection of running backs? If one looks HERE, one can see the 52 running backs who participated in at least 100 plays this past season. The top seven backs have already been noted. Just off the very top we see two backs from New Orleans. Reggie Bush was ranked 41st in rushing yards this season, but 11th in RB Score. Deuce McAllister was 20th in rushing yards, but 15th in RB Score. Coupled with the performance of quarterback Drew Brees, we can see how the Saints improved so much in 2006.

The Saints backs were among the best. What do we see when we look at the worst? If we look at the end of the list we see a surprising name, Shaun Alexander. Alexander’s 2005 performance appear on the top 40 list of RB Score. In 2006, though, his final RB Score was only 2. That’s not his ranking, that’s his total RB Score. So that’s quite a drop off.

Inconsistency is not unique to Alexander. As has been noted in this forum, quarterbacks are inconsistent. Less than 20% of a quarterback’s QB Score per play can be explained by what the quarterback did last year. For running backs it’s the same story. When we look at running backs we again see that less than 20% of current performance – measured with RB Score per play – can be explained by what the running back did last year. And this is the same story we see when we turn to the metrics for running backs developed by Football Outsiders.

For Alexander, injury seems to have impacted his performance. But we can imagine that injuries are not the story for everyone. Edgerrin James offered an RB Score per play of 1.44 with the Indianapolis Colts (average is 1.1). With the Arizona Cardinals his per play performance declined to 0.27. Certainly one suspects that it was the talent difference between the Colts and Cardinals that contributed to the drop-off in the productivity of James.

The list of best and worst is fun, but the consistency story is the real tale to be told. Like quarterbacks, a running back depends on the players around him to perform. So when we look at each back’s stats we are not seeing a measure of that player’s talents, but also the talents of his offensive line (and quarterback, receivers, and coaching staff). In sum, stats in football – unlike baseball or basketball – do not measure individual performance very well. Of course, that story should not detract from the fun we have looking at these numbers.

– DJ

Posted in: Football Stories