If you only had one stat available and you had to pick between two different running backs, you'd probably want to know how many yards each runner averaged per carry. A player's rushing yards is largely a function of his total carries, and that number is dependent on certain things beyond his control (the quality of the other RBs on the team, his coach's philosophy, and the scoreboard, for example). But yards per carry helps to level the playing field, and gets at exactly what we want to know.
Fortunately, we have lots of statistics available, so we don't need to use only yards per carry. So if you were building an NFL team you'd take Clinton Portis before Rock Cartwright, despite Cartwright's 3.0+ advantage in yards per carry last season.
This gets us to the problem of small sample sizes. When Shawn Bryson averaged 5.28 YPC on 50 carries in 2004, it was easy to dismiss his success. Many would claim that achieving a high yards per carry average on a small number of carries is easy. (Of course, when Willie Parker rushed for 5.81 YPC on 32 rushes, those people probably said he wasn't as good as his numbers either.)
You'll hear this argument a lot: it's easy to record a high YPC if you don't have many carries. Maybe they don't really mean easy, but at least easier. But just because people say it, doesn't make it true. It's undoubtedly true that it is easier to get all sorts of extreme YPC numbers with a small number of carries, and that includes really high (and really low) YPC averages. And RBs that are running well usually get more carries going forward than runners that don't do so well. So what do the numbers say?
Carries 2002 2003 2004 2005
01-50 3.92 3.75 4.01 3.34
51-100 4.34 3.86 4.18 4.15
101-150 3.93 4.26 4.11 3.78
151-200 3.88 3.97 4.17 3.87
201-250 3.94 4.11 4.11 3.97
251-300 4.28 4.48 4.19 4.14
301+ 4.41 4.43 4.36 4.49
Average 4.15 4.18 4.19 4.07
The above table includes every RB's YPC average the past four years. If a RB had 87 carries, his totals were put in the "51-100" category. Some of these groups are really small -- in 2003, only three RBs had between 251-300 carries. The low carry group is by far the biggest, because about 80 RBs a year have 50 carries or less. Most of the other groups have between 10 and 25 players.
So what does this table tell us? The RBs with the fewest carries also have the lowest yards per carry average. Now be careful. This does not mean that it's harder for RBs with fewer carries to obtain a high YPC average. It just means that RBs with fewer carries also tend to average fewer yards per carry. They also may have a higher YPC average (more on that tomorrow).
As you could probably noticed, the NFL average jumps around a bit. The average YPC is relatively constant so it's probably not absolutely necessary to normalize each player's production by year, but it feels like the right thing to do. Here's the same data as above but instead of showing each group's average YPC, we're looking at each group's average YPC as a percentage of the league average yards per carry.
2002 2003 2004 2005
01-50 94.4% 89.6% 95.8% 82.1%
51-100 104.6% 92.2% 99.7% 102.1%
101-150 94.5% 101.8% 98.1% 92.9%
151-200 93.4% 94.9% 99.5% 95.2%
201-250 95.0% 98.2% 98.0% 97.6%
251-300 103.2% 107.2% 100.0% 101.7%
301+ 106.2% 106.0% 104.0% 110.2%
I think that table captures what we want a bit better. The runners with the fewest carries clearly average the fewest yards per carry. The RBs with the most carries also average the most yards per carry.
So what does this all mean? Well, it might not mean much. It's logical to assume that coaches give the most carries to the best RBs. Less talented RBs won't get as many carries, and we shouldn't expect them to do well just because they are only running two or three times a game. Something else might skew the data as well. If Joe Scrub is lucky enough to rush 120 times for 600 yards, his coach might give him an extra 40 carries. Even if he only averages three yards per carry on those additional touches, his YPC for the season will be 4.50, and he'll be in the 150+ bracket. So the RBs in the 150+ bracket will get a boost while the RBs in the 101-150 group will "lose" Joe Scrub's stats.
Now that we know it's not common for running backs to average a high number of yards per carry without a lot of carries, let's take a quick look at all RBs last year that averaged at least 4.5 yards per carry with fewer than 100 rushes.
Name Car Yards YPC
Rock Cartwright 27 199 7.37
Jason McKie 3 22 7.33
Dan Kreider 3 21 7
Aveion Cason 10 65 6.5
Darren Sproles 8 50 6.25
Michael Pittman 70 436 6.23
Michael Turner 57 335 5.88
Justin Fargas 5 28 5.6
Terry Jackson 2 11 5.5
Damien Nash 6 32 5.33
Maurice Hicks 59 308 5.22
Adrian Peterson 76 391 5.14
Ron Dayne 53 270 5.09
Ryan Moats 55 278 5.05
Bryan Johnson 1 5 5
Shawn Bryson 64 306 4.78
Leonard Weaver 17 80 4.71
Bruce Perry 16 74 4.62
Mack Strong 17 78 4.59
Chris Perry 61 279 4.57
B.J. Askew 13 59 4.54
Patrick Pass 54 245 4.54
Darren Sproles, Michael Turner, Justin Fargas, Maurice Hicks, Adrian Peterson, Ryan Moats, Leonard Weaver and Chris Perry are all young and talented runners that haven't earned much playing time yet in the NFL. All play behind some pretty good runners, but are only an injury away from seeing significant playing time.
Michael Pittman, Ron Dayne and Shawn Bryson are NFL vets that have seen some success after changing teams, but have had generally underwhelming NFL careers. Bryson and Pittman are both versatile RBs with career YPC averages of 4.0+ and soft hands, but neither looks to be a starter anytime soon.
There's only one RB on that list that is a projected starter in 2006, and it's Ron Dayne. Dayne's always been a controversial running back that seems to polarize NFL fans. Will he revive his career in Denver? Should we care more about the much larger sample size (most of his career in New York where he was a bust) or the significantly smaller but more relevant one (his success playing in Denver last year)? It's hard to say, and I don't think he was as impressive as his 2005 stats indicated, but the above data makes me think we probably shouldn't dismiss those numbers too quickly.
This entry was posted on Sunday, July 9th, 2006 at 11:06 pm and is filed under General, Statgeekery. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.