RB Performance with Age

As promised, today we are going to look at how running backs perform per age. First, we added up all the yards gained by 20-year-olds, 21-year-olds, 22-year-olds, etc, then divided by the number of carries for each age group. The figure below shows the results.

The only 20 year old to play RB in the last three years, is Gary Russell, who I have never heard of either. His three yards per carry in his rookie season is what is bringing down the chart on the left-hand side. After peaking at age 24, players gradually decline until age 30, where there is an unexpected upturn that I am starting to refer to as the "Fred Taylor Effect."

The best explanation I can come up with for the Fred Taylor Effect is that only the best running backs are kept around after age 30 - a mediocre back will get replaced by a cheaper, higher upside, rookie.

Now lets take a look at average player improvement at each age. Values over 1 in the chart below indicate improvement, and values under 1 indicate that the player's performance dropped.


This is my favorite chart so far, because it is the closest to the trend I originally expected. Again, Gary Russell was responsible for the initial dip (as he was the only 21-year-old to have 20-year-old statistics), but the peak improvement at age 24 and 25 make a lot of sense. Then players tend to stay about the same until age 29, when they drop off. Again, the Fred Taylor effect kicks in as players pass age 30.

Note that the improvment past age 30 can't be explained by merely saying that only the best back is kept around past age 30, because these guys are actually getting BETTER after they are supposedly past their prime. Still, I think this is a statistical anomaly in recent stats brought on by Fred Taylor, Ricky Williams, et. al.

Up next, we will try to determine which of these plots we have looked at would have resulted in teh best predictor of 2009 performance.

RB Improvement with Experience

OK, here's the update - I've got the last three season's (2007, 2008, and 2009) worth of games into my database and I can finally start to play around with some stats.

So now the question becomes, what is the best way to project a player's improvement?

I'm starting by looking at running backs and yards per carry. I am breaking down everything by years of experience. In the chart below, I added up all the carries for first year players, then added up all the yards that first year players gained, then divided yards by carries to get yards per carry for first year players. Then I did the same for second year players, third year players, etc.

The first 8 or 9 years of this chart looked like I expected, but there is a very unexpected spike in year 10. This is due to some pretty good year 10's lately from Fred Taylor, Sammy Morris, Kevin Faulk, and Ricky Williams. Those guys also got many more carries than other year 10 guys, so the average was heavily weighted towards their performances.

So to take the number-of-carries bias out of the equation, I just decided to average up all the individual yard per carries for each year of experience. That looked like this:

Hmmm... same shape, just the numbers are a little lower, owing to the fact that guys with better yards per carry tend to get more carries.

OK, lets try another approach. Lets see how individual players improve from year-to-year with experiance. In other words, how much does the average year 2 player improve over his year 1 performance, how does the average year 3 player improve over his year 2 performance, and so on.

Well, we're just not going to get over the late-career bias in this one, but I still think this one might turn out to be the most useful. This would give us the ability to use last season's stats to project a player's performance in the next season. However, no way I am projecting huge improvements for running backs going into years 9 and 10. (Sorry, LaDainian.)

Up next, we will look at the same charts ordered by age as opposed to experience, then we will look at ways to figure out which method is the most accurate.

Another interesting idea, if we have time, is to use a player's total carries entering a season to predict performance.

Firing up again(?)

Wow. Did I really take a whole season off? My performance in my fantasy leagues this year tells me... yes.

So I head into this off-season determined to get my projections ready for 2010, which basically means starting now.

I have the last 3 year's stats (2007, 2008, and 2009) into a new projection program that I am writing. I am still working on the user interface a bit to be able to view complete player profiles, then I should be able to get it to spit out some pre-free agency projections.

I got so burned out after the 2008 season that I will be doing things a bit differently this season. So I will be making fewer posts, but focusing on what I am best at, which is draft preparation. I will check in from time to time as I hit significant strides with the software, and will of course post my projections and draft strategies as the summer wears on.

By the way, am I high again on Jay Cutler? Of course I am!!! I can't wait to nab him in the 10th or 11th round of the 2010 draft and watch him put up big numbers in Mike Martz's offense.