In Part II of this series, I look at whether or not you can tell how a running back will do on the year based on his Week One performance. Last week, we discovered that you can project much of a quarterback's season based on his opening week. Is the same true for running backs?
In a word, no. A running back's yardage opening day only has a 0.39 correlation with his per game average on the year. This correlation is not negligible, but it indicates that simply looking at a running back's performance opening day will not tell you all that much about his performance over the course of the year. Quarterbacks' QB rating, by contrast, has a 0.71 correlation with their overall year performance.
Another way to look at how unreliable opening week numbers are is by examining the degree to which that first game's numbers deviate from the average. On average, running backs' first game performances last year were 20.8 yards away from what their per game average ended up being. Some noteworthy examples: LaDainian Tomlinson- Week 1: 25 yards. Season average: 92.1 yards. Joseph Addai- Week 1: 118 yards. Season average: 71.5 yards. Jamal Lewis- Week 1: 62 yards. Season average: 89.6 yards.
What accounts for this phenomenon? Running back carries are far more vulnerable to strategy changes than are quarterback stats. A new running back could start performing well, and you don't have to bench the starter in order to make room. You simply give the new guy more carries. If a running back gets a minor injury, another running back can give him rest time. If a running back is slumping, his carries may decrease for a couple of games, only to be increased again later. In other words, the life of a running back has many ebbs and flows throughout the course of the year, whereas statistics demonstrate that a quarterback's season is more consistent.
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9 years ago
2 comments:
What about in terms of YPC? Total yards is usually most dependent on whether a RB's team is ahead or behind in the 4th quarter, which has more to do with the passing game and defense. YPC isolates the RB's performance from the other dimensions of the game. It might show more consistency.
I looked at that to see if it would provide more insight, but the relationships were pretty much the same.
The situational component certainly figures into things, but it didn't seem to factor into this, for whatever reason. It could just be that with the ebbs and flows of NFL rushing, one week is simply never an adequate sample size.
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