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Analyzing Felix Jones' Usage, Efficiency on Turf vs. Grass | The DC Times

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Analyzing Felix Jones’ Usage, Efficiency on Turf vs. Grass

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Jonathan Bales

About a year ago, I posted a study which showed that the efficiency of running backs does not change based on the field surface, even for runners of different styles, i.e. as a whole, small, quick running backs perform no better on turf as compared to grass.  I floated out the idea that a running back like Felix Jones (and now rookie DeMarco Murray) might be superior on turf because his quick-twitch, speed-based game seems to be suited for a fast track.  The evidence seemed to suggest otherwise.

Now that Jones has played three seasons in the NFL, his numbers on turf and grass are beginning to become statistically significant.  Of the 38 games in which Jones has participated (including two playoff games), 26 of them have been on turf.  On the chart to the left, you can see his efficiency on runs has remained steady regardless of the surface–he averages 5.3 yards-per-rush on both grass and turf.  He has been a bit superior as a receiver while on grass, but this is likely due to a small sample size (14 receptions on grass, 58 on turf).

While the numbers related to Jones’ efficiency are no surprise, his usage statistics are another story.  You can see that Jason Garrett has given Jones three more carries per game when the Cowboys have played on turf as compared to grass.  This may not seem like a lot, but a roughly 30 percent increase over a sample size of 38 games is pretty significant.  The probability that such a difference would be due to chance is small, meaning it looks as though Garrett provides the ball more to Jones when the ‘Boys play on what the coach considers a fast track.

That idea appears to be affirmed by Jones’ reception numbers as well, as he catches nearly twice as many balls on turf over grass.  While Jones is the recipient of dump-offs from time to time, the majority of his receptions have come on screens or other plays designed to get him the ball in space.  It really does appear as though Garrett assumes Jones is a more lethal player on turf.

Of course, the Cowboys play their home games on turf, and the team may be more likely to be winning late in home games over road games.  When leading late in the game, additional carries are likely.  However, in the 20 home games in which Jones has participated, the ‘Boys are just 11-9.  That mark is very similar to the Cowboys’ 10-8 mark on road games in which Jones has played, meaning the idea of Jones’ “extra” turf carries coming from leading late in home games is inconsistent.

Ultimately, Garrett just needs to continue to feed Jones the football, regardless of the playing surface.  The addition of DeMarco Murray via the draft provides the Cowboys with an insurance policy against a Jones injury.  Of course, Garrett may have no choice but to give Jones or Murray plenty of touches on grass, since Marion Barber will be out of Dallas in 2011 and the head coach loathes Tashard Choice.

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5 Responses to Analyzing Felix Jones’ Usage, Efficiency on Turf vs. Grass

  1. Greg K says:

    You said something very important which seems to be an on-going cognitive distortion on the part of Jason:
    “It really does appear as though Garrett assumes Jones is a more lethal player on turf.”
    That’s all fine and good if the defense is unaffected by the surface difference. But they can’t be – it can’t be just Felix who varies because of surface differences. Then again, Garrett has such a bizarre self-serving scheme bias that his plays will work on any system or any defensive attack, that I don’t think he realizes that the defense is a real entity.

    So my point is: perhaps, just perhaps, defensive players who based their game on speed and dexterity (like safeties, LBs, and 4-3DEs) ALSO are more lethal and faster on turf. It might mean that the lanes close quicker, the pressure comes faster, and the blitz looks might be more frequent (which would explain the dump-offs). To paraphrase one of the best quotes from The Incredibles: “If all players are more lethal on turf, than none of them are.”

    Therefore, Felix might have more of a chance for better gains when that strange ubiquitous presence known as the opposing defense cannot accelerate (i.e. are less lethal) as well on the grass surface and the lanes and openings have a greater lifespan.

  2. Tyrone Jenkins says:

    My man Greg found a way to slip ubiquitious into a post – very nice…

    To his point, though, there’s more to the story. Essentially, from a statistical standpoint, you can look at a plethora (like that one) more variables wrt efficiency of a RB vs the defense. Everything from the padding under the turf to the brand of shoe and/or spike length to the “lack” of adverse weather that tends to be prevalent w/ turf fields (which are usually inside).

    Point I’m making is that sooner or later, you have to “assume” some of that stuff away as being equal to both sides.

    Turf vs. Grass is an interesting one – one that I think there IS a difference. I doubt anyone would disagree that Barry Sanders would probably be more effective running w/ better footing (allowing him to change direction even quicker). The same argument applies for Felix. If a guy who runs a 4.35 on turf but runs a 4.40 on grass, he’s more effective than a guy who runs a 4.55 on turf but runs a 4.60 on grass. Even though the difference in speed in both instances is .05, the greater advantage goes w/ the difference from 4.35 to 4.4 because there’s a “steeper” advantage to be gained at the TOP end of speed. Ask any drag racer this.

  3. willis says:

    good point about top end speed there.

    JBales – since there is kind of a lull in news/new information now that the draft is over, how about a draft grade for each team, just for fun. If its too much work to get an in depth analysis on all 32 teams, how about just the NFC east.

  4. Greg–Hell of a comment. Really agree with what you said here, and if you run through the archives on this site you’ll see a lot of work dedicated to showing, as you put it, “Garrett’s self-serving scheme bias.” Could not agree more. Check out the stats from Double Tight Strong if you have not yet (search for it in the top right).

    Tyrone–The reason I did this was because there seemed to be no statistical difference between RBs AS A WHOLE on grass vs turf. I wanted to see if that was due to differences leveling out or no actual deviation from player to player. Jones’ numbers seem to suggest the latter is true, at least for him, although we definitely need more numbers. Your point about the .05 second difference between varying constraints is well-taken and I agree with it.

  5. Willis–A draft grade for each team would be impossible (at least one which I felt confident about), but NFC East is very workable…I will get it up this week.

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