People play fantasy sports for many different reasons. Some play it to win money, others to earn honor or bragging rights, and others as an analytical hobby and mathematical pastime (gestures self-deprecatingly to numberFire staff).

I, like many others, find joy in a fourth route to fantasy sports: I play to simulate the experience of being an NFL general manager. While many like to embrace the idea of fantasy football as just that -- a fantasy -- I find joy in putting myself to the challenges that real roster builders might face.

Chief among those is the expansion from playing with team defenses to Individual Defensive Players (IDP).

IDP is rapidly gaining ground in fantasy circles as no longer just for the “hardcore”, but something that any fan of football can appreciate. If you’ve been a fantasy player your whole life, but your favorite players are defensive ones, how will you have the same satisfaction on draft day as the guy wearing the Aaron Rodgers jersey? You won’t, unless you delve into the world of IDP.

This seems to be a very different format to standard team defense leagues, so where do you start? Fortunately, the numberFire staff -– and our handy-dandy Draft Kit -– is here to help you plan or draft your first IDP league. This first installment in our IDP content will deal specifically with how players and positions are affected by defensive schemes.

Defensive Line

Before a body can start flexing muscles, it has to have a basic understanding of what those muscles do. And before it can really understand what those muscles do, it has to understand the skeleton they’re stretched over. In IDP fantasy football, that means knowing defensive schemes and how their structures affect player and positional values.

I wrote an article this offseason on how defensive schemes affect team defensive production, breaking the study down into defensive fronts and defensive styles. For a short summary here, the defensive front describes the look and basic assignment of the defense: 4-3 means there are four down linemen, three stand-up linebackers; 3-4 means three down linemen, four stand-up linebackers. The two main positions we deal with in the defensive are the defensive tackle (or interior defensive lineman) and defensive end. How does scheme affect positional value on the defensive line?

The table below shows a few categories -– drawing from 2014 balanced scoring fantasy results -– which we can examine to see the value of positions in different base fronts. We will compare the 4-3 and 3-4 in average points among the highest scoring players (top 15) at the position, the average standard deviation for that front’s fifteen highest scoring players, and how many players from that front were in the top fifteen of the position. What do we find?

For the two defensive line positions, there’s no two ways about it: the 4-3 is more prolific for these players. In raw points as well as top-end scoring, 4-3 defensive tackles and defensive ends greatly outpace their 3-4 counterparts. The standard deviation is the amount from a weekly average that each scheme deviates; here, too, the 4-3 defensive end outdoes the 3-4 version. However, the 3-4 defensive tackle actually has a lower variance than his 4-3 opposite. With this lower-scoring position in general, though, one hopes for upside; we still would prefer a 4-3 player here.

The reason for this is that many 3-4 teams run a two-gap assignment, meaning that each down lineman is responsible for controlling two gaps between offensive linemen. Many 4-3 teams, however, use one-gap assignments, so each player is allowed to attack the offensive line and aim for sacks or tackles for a loss. More opportunity almost always equals more production.

What about the linebackers?

Linebackers

The table below here shows the exact same study as for the defensive line, but this time we are cracking into the linebacker corps of these defensive fronts. We again separate them both by defensive front, and by inside or outside designation. Which is more prolific for fantasy purposes: the 4-3 or the 3-4?

Most analysts recommend using 4-3 linebackers in almost any situation, but the data doesn’t seem to support that in this day and age of the 3-4 pass rusher. One explanation for the supremacy of the 3-4 outside linebacker is that they have a much higher upside for sacks in today’s game, and defensive coordinators are calling more complicated blitz packages than ever before. This kind of upside, though, should be marked with a higher weekly variance than the 4-3 outside linebackers; why isn’t it? It’s possible that the prevalence of strong line play in 4-3 schemes limits steady tackle opportunities and the 4-3 outside linebacker thrives on coverage and open-space mobility to make tackles.

Similarly, we see the 3-4 inside linebacker surpasses the 4-3, as well. Many suggest that the 4-3 inside linebacker is the best fantasy option because of the stable floor of points one can expect from them, as well as little competition for other tackle opportunities. However, the fact is that four down linemen limit the number of tackle opportunities coming through for linebackers to make. With only one defensive tackle in a 3-4 scheme plugging the gaps, there’s statistically a better chance for a 3-4 inside linebacker to rack up tackles than a 4-3 one.

There are always exceptions to all of these rules, though. J.J. Watt is the best defensive player in the league by far, and he transcends the deficiencies natural to a 3-4 defensive end. Similarly, Luke Kuechly, Lavonte David, and DeAndre Levy have the stellar ability to make plays on the ball as 4-3 linebackers, and they all rank in the top-six from last season. The only thing is that ten of the next 12 linebackers play in 3-4 schemes.

Defensive Backs

Defensive backs are a bit of an interesting beast. By far the least productive fantasy unit on a consistent basis, these players are less affected by schemes and more so by matchups. Coverages vary from play to play, and weekly game plan to weekly game plan, so it’s not as if there are two clearly defined defensive back schemes like the 4-3 and 3-4. On most plays, also, the defensive back is in coverage, meaning that most opportunities they have to defend a pass, intercept a ball, or make a tackle are dependent on the quarterback throwing it their way. This is why elite NFL cornerbacks such as Darrelle Revis and Richard Sherman are often terrible fantasy options; no one wants to put the ball near them if they can help it.

The table below does show the averages of the top-30 cornerbacks and safeties, both in terms of total points and standard deviation. The 30 total of each position accounts for the combined 30 of each scheme and position before. What do we find?

Safeties, it should be noted, score more on average than their cornerback brethren. This comes back to the idea of play opportunities: a cornerback - whether in zone or man coverage - is reliant on the ball coming to them. Safeties at least sometimes play in run support and come on blitzes. When looking at defensive backs, scheme doesn’t change much but we should give preference to the safety.

Scheme influences how to value positions in IDP very much. Once we look at the numbers, though, it begins to be clear how to approach IDP players. We’ll look more into comparing the value of positions against each other in a future article, but for now we’ve begun to look at the nuts and bolts of how to understand defensive fantasy football.