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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.

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