The Fake Stuff

Being a sports fan is all about good-natured disagreement. Who's the greatest running back of all time? If I say Barry Sanders, I've got hundreds of readers calling me an idiot because it's clearly Jim Brown. If I say Brown, the Payton fans are in disbelief. Who's going to win the Super Bowl this year? What was the greatest team of all time? Should we blow up all the on-field instant replay machines? Any of these questions will get you an argument, and that's why we, as sports fans, ask them so often. But there is one issue on which sports fans agree totally and completely without reservation:

Artificial turf sucks.

I can write that without any fear of angry emails. It's not controversial at all. The one common bond that unites sports fans across the world is hatred of fuzzy green parking lots. But maybe it's good for something. In particular, maybe we can use it to get an edge for our fantasy squad. This article will examine how running backs perform on grass vs. turf.

First, some summary numbers. I looked at all running backs who played at least 10 games during the period 1997-1999, and I totalled their performance on grass and turf. I'm interested in the running game here, so I've just listed rushing yards, rushing TDs, and rushing fantasy points (rushing yards/10 + 6*rushing TDs). Here's the data:

        rushes   yards    TD    rushing FPT
-------------------------------------------
Grass    17918   71101   488       10038
Turf     16559   65956   438        9224
Our brains aren't really wired to handle that kind of data, so let's look at it in terms of average per carry.
  
            Yd/Rush   TD/Rush   FPT/Rush
-----------------------------------------
Grass        3.968     .0272       .560
Turf         3.983     .0265       .557
That's what I call close. In terms of fantasy points per rush, there is no practical difference at all between how runners have performed on turf vs. grass. Grass actually comes out slightly ahead of turf, which is mildly surprising.

That's not the whole story though. For those of you who enjoy brain teasers, try this one on for size: it's possible that every single runner in the entire NFL performs better on turf than on grass, yet the overall grass stats are better than the overall turf stats. How's that? Well, consider an NFL with only two running backs, and suppose they amass the following numbers:

               ---- Grass ---   ---- Turf ---
               Rush      FPT    Rush     FPT
---------------------------------------------
Eddie George    100      150      10      20
Jon Witman       10        2     100      30
---------------------------------------------
TOTAL           110      152     110      50

Note:  these numbers were completely fabricated for demonstration 
purposes.  
Both George and Witman were better on turf than on grass, yet the overall grass stats look much better. It turns out that way in this simplified NFL because the running backs that played most often on grass were simply better backs. Could the same bias be affecting the overall NFL data we saw at the top of the article?

To get a handle on it, let's look at how many individual backs were better on grass and how many were better on turf. Below, you'll find a list of all backs who had 100 or more carries on both grass and turf over the past three years. Next to each name, you'll see his rushing fantasy points per carry over the same period on both grass and turf.


DIFF = FPT per rush on grass  -  FPT per rush on turf

(so negative means better on turf, positive means better on grass)
                        +-----------+
                        |  Fant Pt  |
                        |  per rush |
                        +-----+-----+
LastName     FirstName  |Grass| Turf| DIFF
------------------------+-----+-----+-----
Hoard        Leroy        .44   .97  -.53
Hill         Greg         .39   .65  -.26
Smith        Antowain     .43   .64  -.22
Levens       Dorsey       .49   .69  -.19
Smith        Robert       .48   .67  -.19
Kaufman      Napoleon     .54   .66  -.13
Staley       Duce         .42   .52  -.11
Anderson     Jamal        .51   .60  -.10
Dunn         Warrick      .42   .51  -.09
Alstott      Mike         .57   .66  -.08
Means        Natrone      .52   .59  -.07
Sanders      Barry        .61   .68  -.07
Davis        Stephen      .68   .75  -.07
Dillon       Corey        .57   .62  -.04
Watters      Ricky        .49   .53  -.04
Bettis       Jerome       .49   .51  -.02
Wheatley     Tyrone       .55   .57  -.02
Holmes       Priest       .61   .63  -.01
Edwards      Robert       .56   .57  -.01
Davis        Terrell      .75   .76  -.00
Martin       Curtis       .49   .49  -.00
Brown        Gary         .49   .49   .01
Way          Charles      .60   .57   .02
Lane         Fred         .56   .54   .03
Murrell      Adrian       .49   .45   .04
Smith        Emmitt       .64   .59   .05
George       Eddie        .53   .47   .06
Allen        Terry        .53   .47   .06
Faulk        Marshall     .64   .57   .07
Harris       Raymont      .57   .48   .09
Abdul-Jabbar Karim        .54   .44   .10
James        Edgerrin     .76   .59   .17
Garner       Charlie      .70   .52   .18
Taylor       Fred         .80   .62   .18
Hearst       Garrison     .65   .45   .20
Warren       Chris        .76   .53   .23
Bates        Mario       1.04   .60   .44
There are 37 backs here. 21 of them were better on turf and 16 were better on grass, but the overall difference is practically nil. Specifically, the average DIFF is -.008.

Of course it is possible that the playing surface affects different kinds of runners in different ways. Barry Sanders and Warrick Dunn are frequently cited as guys who are (were, in Barry's case) better on turf -- the general implication being that runners who depend on shiftiness and cutback ability get an extra boost from the better traction turf provides. But the above list does not bear that out at all. There are plenty of power backs at the top of the list, including the biggest turf-hound of them all: Leroy Hoard. Likewise, the bottom of the list (the grass-lovers) contains plenty of small quick backs.

In fact, in terms of styles, there doesn't seem to be any pattern at all to the list. This is an indication that "ability to run better on turf" and "ability to run better on grass" are not really abilities at all. I strongly suspect that simple random chance ordered that list and that it has no predictive value whatsoever. If we re-do this list after the 2000 seasons, it's just as likely to be flipped upside down as stay where it is.

Summing up, I think we have pretty strong evidence here that playing surface should play no role whatsoever in determining which running backs you draft or which ones you start. Turf may give running backs better traction, but it also gives defenders better traction, and apparently it evens out.