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Todd Gurley, Jay Ajayi, and Running Back Variation

In yesterday’s post about Frank Gore, I lauded Gore’s remarkable consistency, year after year. But his consistency — for better or worse — is also true game after game. Gore pulled off a tough feat in 2015, rushing for 967 yards while failing to record a single 100-yard game. Last year, he rushed for 1,025 yards and while he topped the century mark twice, he gained just 101 and 106 yards in those games.

How consistent is Gore? Well, not as consistent as Todd Gurley (again, for better or worse: consistency is neither inherently good or bad). I looked at all running backs who averaged at least 50 rushing yards per game and had 700 rushing yards last year. In the graph below, on the X-Axis I have plotted rushing yards per game; on the Y-Axis is each player’s standard deviation in rushing yards across all 2016 regular season games. Gurley, as you can see, is the “lowest” on the graph, although he’s also really far to the left (because his average wasn’t very high). In general, the running backs who gain more yards are less consistent, which is just a residue of how standard deviation works. One interesting counter to that: Ezekiel Elliott.

But Gurley’s standard deviation was extraordinarily low, even for someone who averaged only 55 rushing yards per game. Take a look at how game logs, from best to worst: he finished with between 33 and 85 yards in every game last year!

 
Rushing
Rk Date G# Opp Result Att Yds
1 2016-09-25 3 TAM W 37-32 27 85
2 2016-11-20 10 MIA L 10-14 20 76
3 2016-10-09 5 BUF L 19-30 23 72
4 2016-12-24 15 SFO L 21-22 23 67
5 2016-11-13 9 NYJ W 9-6 21 64
6 2016-12-11 13 ATL L 14-42 16 61
7 2016-10-16 6 DET L 28-31 14 58
8 2016-10-23 7 NYG L 10-17 15 57
9 2016-09-18 2 SEA W 9-3 19 51
10 2016-11-27 11 NOR L 21-49 13 50
11 2016-11-06 8 CAR L 10-13 12 48
12 2016-09-12 1 SFO L 0-28 17 47
13 2017-01-01 16 ARI L 6-44 14 40
14 2016-12-04 12 NWE L 10-26 11 38
15 2016-12-15 14 SEA L 3-24 14 38
16 2016-10-02 4 ARI W 17-13 19 33
16 Games 4-12-0 278 885

On the other end of the spectrum is Jay Ajayi.   The Dolphins running back had 3 games with 200+ yards and only 1 other game with 80+ yards.

Rushing
Rk Date G# Opp Result Att Yds
1 2016-10-23 7 BUF W 28-25 29 214
2 2016-12-24 15 BUF W 34-31 32 206
3 2016-10-16 6 PIT W 30-15 25 204
4 2016-11-06 8 NYJ W 27-23 24 111
5 2016-11-13 9 SDG W 31-24 19 79
6 2016-11-20 10 LAR W 14-10 16 77
7 2016-12-04 12 BAL L 6-38 12 61
8 2017-01-01 16 NWE L 14-35 16 59
9 2016-12-17 14 NYJ W 34-13 19 51
10 2016-12-11 13 ARI W 26-23 20 48
11 2016-11-27 11 SFO W 31-24 18 45
12 2016-10-09 5 TEN L 17-30 13 42
13 2016-09-29 4 CIN L 7-22 6 33
14 2016-09-25 3 CLE W 30-24 7 28
15 2016-09-18 2 NWE L 24-31 5 14
15 Games 10-5-0 261 1272

Four years ago, I wrote about how Jamaal Charles had one of the most inconsistent fantasy seasons ever.   Ajayi’s 2016 is pretty darn close.  There, I looked at fantasy points, but in pure rushing yards, Charles had a standard deviation in 2012 of 71 rushing yards; Ajayi had a standard deviation of 68 rushing yards in 2016.

  • AgronomyBrad

    I would imagine that standard deviations would be similar for per-carry rushing yards? Seemed like Todd Gurley didn’t break many long runs, but Ajayi had a lot of “boom-or-bust” attempts (full disclosure, I didn’t watch many LA or Miami games, but this seemed to be the narrative).

    • AgronomyBrad

      Just did some quick calculations on each of their highest-attempt games from this past year (Gurley @ Tampa Bay, Ajayi @ Buffalo) and Gurley’s was 3.7 and Ajayi’s was 10.1

    • Richie

      Just out of curiosity, I pulled the numbers for Ajayi and Elliott.

      For Ajayi:
      Average 4.87 yards
      Median 3 yards
      Mode 2 yards
      50+ carries: 3 (one per 86 carries)
      40+ 4 (one per 65 carries)
      30+ 6 (one per 43 carries)
      20+ 10 (one per 26 carries)
      10+ 38 (one per 6.8 carries)
      5+ 95 (one per 2.7 carries)
      under 5 yards: 103 times (one per 2.5 carries)

      Elliott:
      Average 5.06 yards
      Median 3 yards
      Mode 2 yards
      50+ 2 (one per 161 carries)
      40+ 3 (one per 107 carries)
      30+ 5 (one per 64 carries)
      20+ 14 (one per 23 carries)
      10+ 48 (one per 6.7 carries)
      5+ 118 (one per 2.7 carries)

      under 5 yards: 132 times (one per 2.4 carries)

      This surprises me. I thought Ajayi was more boom-or-bust than Elliott. This is true, but the magnitude isn’t much. He was much more boom than Elliott, but only slightly more bust than Elliott.

      Looks like the main difference is that Ajayi bunched his booms into a few games, while Elliott was more consistent from game-to-game.

    • JeremyDeShetler

      Did a quick look at their 2016 carries. Ideally I would look at down/distance too, but don’t have time.

      For carries of 6 yards or more, Ajayi was 32%, Gurley 18%.
      For carries of 10 yards or more, Ajayi had 39 carries (15%), Gurley 16 (5.7%).

      For a distribution,
      Ajayi on 259 carries, 23.5% were for no gain or a loss, 32% for 1-3 yards, 20% for 4-7 yards, 15.5% for 8 to 12, and 8% were 13 or more.
      Gurley on 278 carries, 22.3% were for no gain or a loss, 42% for 1-3 yards, 23% for 4-7 yards, 10% for 8 to 12, and 3% were 13 or more.

  • Lobo_Marino

    I think calculating the coefficient of variation (st.Dev/average) in this would be way more telling. Of course that low distance runners would have a lower st.dev than those who run more. Coefficient of variation helps in seeing about how much a player deviates from his usual.

    • Lobo_Marino

      Also, graphs should ALWAYS be labeled, even if you describe them in the text.

  • Pingback: Todd Gurley was the most consistent RB in 2016 – patriciaplag7906()

  • Not surprised Ajayi was inconsistent given the inconsistencies of the Dolphins offensive line. Those 200 yard games were the rare instances when Albert, Tunsil, Pouncey, Bushrod, and James were all playing together. Once Pouncey was put on IR and Albert started missing time there wasn’t as much running room. The line consistency extends beyond the running game too. Tannehill and the offense as a whole produce much better with that starting lineup.

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