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The Jerick McKinnon/Matt Asiata Time Share

Last year, I looked at the unusual running back by committee in Arizona in 2013.  Rashard Mendenhall was the team’s primary back, but he averaged 3.17 YPC that season, while Andre Ellington averaged 5.53 YPC. To measure how “unusual” the split was, I came up with the following methodology: calculate the difference between the YPC of the top two running backs (as measured by carries) on each team, and multiply that difference by the number of carries given to the running back with fewer carries. So for the 2013 Cardinals, the difference between Ellington and Mendenhall in terms of YPC was -2.36; we multiply that by 118 to get a value of -278. For 2014, the most extreme result along this line came in Minnesota.

Matt Asiata had 164 carries for the Vikings but gained just 570 yards, for a 3.48 YPC average. Meanwhile, Jerick McKinnon rushed only 113 times but picked up 538 yards, a 4.76 YPC average. So McKinnon averaged 1.28 more yards per carry than Asiata. Then, we multiply -1.28 by 113, which produces a value of -145, the most extreme of the 32 teams last year.

The reason for this two-step process is that when dealing with backup running backs, you sometimes get small sample sizes. For example, Latavius Murray averaged 5.17 YPC on his 82 carries, but the Raiders split doesn’t count quite as extreme as the Vikings split based on this method.  Also, the Cowboys split would look pretty funky if you didn’t penalize RB2s that had only a handful of carries:

RkTmRunning BackCarYardsYPCRunning BackCarYardsYPCValue
1MINMatt Asiata1645703.48Jerick McKinnon1135384.76-145
2OAKDarren McFadden1555343.45Latavius Murray824245.17-141
3INDTrent Richardson1595193.26Ahmad Bradshaw904254.72-131
4DALDeMarco Murray39218454.71Joseph Randle513436.73-103
5PHILeSean McCoy31213194.23Darren Sproles573295.77-88
6NYGAndre Williams2177213.32Rashad Jennings1676393.83-84
7TAMDoug Martin1344943.69Bobby Rainey944064.32-59
8WASAlfred Morris26510744.05Roy Helu402165.4-54
9BUFFred Jackson1415253.72Anthony Dixon1054324.11-41
10TENBishop Sankey1525693.74Shonn Greene943924.17-40
11NORMark Ingram2269644.27Khiry Robinson763624.76-38
12CLETerrance West1716733.94Isaiah Crowell1486074.1-25
13NYJChris Ivory1988214.15Chris Johnson1556634.28-20
14CHIMatt Forte26610383.9Ka'Deem Carey361584.39-18
15ATLSteven Jackson1907073.72Devonta Freeman652483.82-6
16DETJoique Bell2238603.86Reggie Bush762973.91-4
17ARIAndre Ellington2016603.28Stepfan Taylor632083.3-1
18SFOFrank Gore25511064.34Carlos Hyde833334.0127
19STLTre Mason1797654.27Zac Stacy762933.8632
20SEAMarshawn Lynch28013064.66Robert Turbin743104.1935
21PITLe'Veon Bell29013614.69LeGarrette Blount652664.0939
22NWEShane Vereen963914.07Stevan Ridley943403.6243
23MIALamar Miller21610995.09Daniel Thomas441683.8256
24GNBEddie Lacy24611394.63James Starks853333.9261
25CARJonathan Stewart1758094.62DeAngelo Williams622193.5368
26DENC.J. Anderson1798494.74Ronnie Hillman1064344.0969
27SDGBranden Oliver1605823.64Donald Brown852232.6286
28JAXDenard Robinson1355824.31Toby Gerhart1013263.23109
29BALJustin Forsett23512665.39Bernard Pierce933663.94135
30CINJeremy Hill22211245.06Giovani Bernard1686804.05171
31KANJamaal Charles20610335.01Knile Davis1344633.46209
32HOUArian Foster26012464.79Alfred Blue1695283.12282

A few comments:

  • Darren McFadden averaged 1.17 fewer YPC than Rashad Jennings in 2013, and 1.73 fewer YPC than Murray in 2014. Make of that what you will, but it will be very interesting to see how McFadden fares in Dallas given that history.
  • We know Alfred Blue was not very effective last year, but this really puts it in perspective. Foster averaged 1.67 YPC more than Blue, the largest differential of any RB1-RB2 combo last season. Blue also had the most carries of any RB2 [1]Defined as the running back who was second among running backs in carries. last year, which is why Houston produced such a large value of “unusualness” under this formula.
  • Not shown: for five teams, their quarterback was actually second on the team in carries. Those five were San Francisco, Seattle, Miami, Carolina, and… Chicago. Ka’Deem Carey had just 36 carries, which is probably a better sign of how much the Bears relied on Matt Forte than Forte’s 265 carries.

References

References
1 Defined as the running back who was second among running backs in carries.
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