Fantasy Theory: IDP Leagues (Individual Defensive Players)

As I was invited to a Dynasty/IDP league, of which I have no knowledge, I had to figure out quickly what is important, who to draft, and what to draft. This is a log of my investigations.

1) What stats are important in IDP?

I remembered that IDP players is generally a fairly deep category, and there is a lot of value; I also remembered vaguely that only a few stats really matter (which is not that different from say RB/WR, where yards is still the main difference maker).

I started with downloading some stats from Pro Football Reference, and mapping them to the settings in this particular league:

As a spoiler alert I already indicate the categories I found are the most rewarding.

I mapped the players to the points, and charted the results.

As you can see, Tackles (Solo/combined) has a pretty good correlation with the points; harder to see is that also Passes Defended is important. I also charted sacks, which was the reason one player (JJ Watts) originally distorted that chart, but it is less important generally than the other cateogries; or at least it's less reliable as a category and harder to plan for.

2) Tackles

I again went to Pro Football Reference, and this time selected based on Tackles, to find the highest scorers. I used a pivot chart to see at which age these players reach their peak, and whether they can be immediately productive - for instance TEs generally need a couple years to produce, QBs can be productive at a high age while RBs score early and decline early. How is this for IDP?

It seems that IDP can be effective immediately when entering the league (Luke Kuechly) and until a late age (London Fletcher). For Dynasty purposes then, these guys are very valuable.

3) Passes Defended

I did the same for passes defended. Interestingly, this gives a quite different type of chart:

While these guys still have long careers, they rarely have 2 top years in a row. One exception is Joe Haden; but Darrelle Revis and Brent Grimes sometimes had years between seasons with high numbers.

Let's take another look at entire career of some of the top guys:

Although it wasn't so easy to see earlier, we can conclude that:

- these guys can have long careers

- there is quite a bit variation from year to year

- There is a slight decline from their entry in the league.

The top 10 pass defenders are all DB. Interestingly, these 10 are not in the top-10 DB's, with the exception of Kareem Jackson. Therefore defending passes is not a crucial factor for IDP, and we can focus on tacklers.

Let's focus again on the tacklers:

4) Tacklers (revisited)

We again look at some of the top tacklers over the past years:

That is a quite different curve, more similar to TEs or WRs; 

- these guys can also have long careers

- there is a lot more consistency from year to year

- There is a clear increase in the early years, and then a decline after age 30.

Now that we have a better view of what's important (Tackles and Passes Defended), let's see if draft position or maybe college stats are any indicator for the performance as IDP.

The top tacklers are all LB, which is why they are more valuable.

5) Positional Value

In IDP there are 3 specific positions (in my league we have 2 of each): Linebackers (LB), DB (Defensive Back, including Cornerback and Safeties) and DE (Defensive End including Tackles).

I gathered the top-100 for each of these three positions, and calculated the points under my league rules. Out of the top players, only one is LB:

Ranks IDP points Player POS
1 291.5 Darius Leonard LB
2 241         Cory Littleton         LB
3 239.5 Luke Kuechly         LB
4 230.5 Blake Martinez LB
5 228         Bobby Wagner LB
6 215.5 Jamal Adams         DB
7 215         Leighton Vander Esch LB
8 213         Telvin Smith         LB
9 211.5 Lavonte David LB
10 209.5 Roquan Smith         LB

The first DE is Danielle Hunter at 29. Nevertheless, it may be worthwhile to draft DBs before LBs:

Above you see the top 100 LBs plotted with the top 100 DB and top 100 DE. We see that the curves for LB and DE are steeper than for DB. Let's focus on the top-30 (in a 14 team league we expect that for each position the top 28 are drafted):

With the added trendlines and equations, we confirm that indeed the steepest curve is for DE, then LB, and finally DB. This means that it is probably favorable to draft DE (and LB) earlier as they have the highest value above replacement.

(However, RB, QB, WR and even TE still have a lot steeper curves. Therefore, it does not make a lot of sense to start drafting IDP before RB/WR25 are off the board; that's around ADP 60 or later. For instance Darius Leonard, break-out player of 2018 is drafted in 2019 in redraft IDP around pick 70.)

6) NFL Draft Position and IDP rookies

Can we predict the stars by looking at the NFL draft? After all, we are playing Dynasty, so we need to predict the future without even having much of a past.

Hm, that doesn't look hopeful; this data is all over the place. However, this includes various positions, so let's see what we get if we limit ourselves:

Nope. Maybe if we zoom in on the first round picks?

Nope. We can't trust the NFL in selecting IDP rookies (similar to many other positions where players have to learn btw). Therefore, it is probably best not to invest too high picks.

7) College Stats and IDP rookies