How to Predict Defensive Production in Fantasy Football

What makes for a great fantasy football defense? It's more than just yards or points allowed.

"Defense wins championships."

If you grew up as a fan of the Steelers or Bears, or recently have been a fan of the Ravens, Buccaneers, 49ers or Seahawks, you or someone you love has almost certainly uttered those words when discussing your favorite football team.

But the defense is often neglected in fantasy football, and not shown the proper respect it deserves as a "championship winner." In fact, some leagues are phasing out the defense in favor of individual defensive players, while other leagues are just scrapping defense altogether and opting for more bench spots for offensive players.

Yes, defenses don't score all that many points, and sure, they're a "onesie" position and are easily streamable. But what if you're in a best-ball league and need a defense for the whole season? What if you're in a league with amped-up scoring for defenses? How do you predict what will make a fantasy defense great?

Our in-house statistic, Net Expected Points (NEP), helps us determine which defenses are the most efficient and effective every season, so let's take a look behind the numbers and see if we can figure out what makes for a good fantasy defense.

2013 Defensive Review

Here is our data from last season, with the fantasy ranking, Adjusted Defensive Net Expected Points ranking (which adjusts for strength of schedule), yards allowed ranking, and points allowed ranking.

TeamPointsFantasy RankNEP RankYards RankPA Rank
Kansas City Chiefs20414245
Seattle Seahawks1952111
Carolina Panthers1933322
Cincinnati Bengals1704236
Arizona Cardinals1665567
San Francisco 49ers1646753
St. Louis Rams1597201513
Buffalo Bills145881020
New England Patriots1449122610
Indianapolis Colts1341023209
Denver Broncos12511131922
Baltimore Ravens1251291212

A quick glance reveals that yards allowed is next to useless in predicting fantasy success, and that points allowed and NEP are much stronger predictors.

It makes sense that points allowed lines up with fantasy scoring, as it's a part of the scoring system for defenses. (I used standard scoring for this research.) But NEP correlated just as well, if not better, with fantasy ranking.

Why is that? Because NEP accounts for sacks, interceptions and turnovers as a part of its calculation of a team's performance, and all of these elements factor strongly into a good fantasy defense. Simply not allowing points doesn't make a defense good, because if it's unable to generate points from turnovers, sacks and touchdowns, it will lag behind.

The 2013 New Orleans Saints are a perfect example of this. The Saints finished the season fourth in points allowed and yards allowed, but were only the 24th-best fantasy defense. Their inability to get turnovers (only 19) and defensive scores (no safeties, no touchdowns) held them back from being a top-flight option in fantasy.

Also, despite the fantasy position being considered "defense and special teams," the special teams aspect only accounts for a small portion of the success for a particular team. The Chiefs were the best 2013 defense thanks in part to four return touchdowns on special teams, but the Vikings and their three special teams touchdowns finished 28th thanks to a limited number of turnovers and a lot of points allowed.

But let's take a look back a little further, and see just how strong the correlation is between an efficient and effective defense and a strong fantasy season.

A Strong Correlation

Since 2010, NEP ranking and fantasy ranking have a correlation of .72. This is stronger than the correlation between yards allowed ranking and fantasy ranking (.42) by quite a large margin, and stronger than even points allowed ranking (.64), despite points allowed being a part of the scoring system.

Of the 24 top-six defenses since 2000, only four finished outside of the top-10 in our Adjusted Defensive NEP metric. All four of those teams scored seven or more touchdowns to compensate for not having as strong of a defense as the other top fantasy performers.

And of the six teams ranked 20th or worse to finish as top-10 defenses over the past four seasons, four scored seven or more touchdowns, while the other two had 40 or more sacks and 27 or more takeaways.

All in all, 75 percent of top-four NEP defenses finished as top-four fantasy defenses.

So what does this mean? Defenses that are productive and efficient consistently perform the best in fantasy football, but that means more than simply looking at which defenses allow the fewest yards or points.

Elite defenses that generate turnovers, get sacks, and score on takeaways are the best fantasy options, and that requires a bit more research than simply sorting the NFL statistics table by yards or points allowed.

A Word of Advice

If you want NEP-based fantasy advice on which defenses you should draft this season, head over to our Fantasy Football Cheat Sheet. However, a quick glance will reveal the most important fact about this position that fantasy owners must keep in mind.

The FireFactor for defenses in a standard league with normal laws and lineups is incredibly low. FireFactor is a ranking mechanism that incorporates value over replacement player principles to help you decide between players of different positions during your draft.

The top defenses simply don't score enough versus the median defenses to justify a high pick in your fantasy draft. In fact, only 12 defenses since 2010 have outscored the average defense by more than three points per game.

So spending a 10th-round pick on the Seahawks to get, at best, a three point per week advantage on even your worst opponents' defenses is a waste of valuable draft assets that could be spent building a strong bench and stocking up trade assets.

But if you've reached the point of your draft where you're stabbing in the dark at unproven and unknown players, and you feel it's time to lock up your defense, stop by the Fantasy Football Cheat Sheet, and get some NEP-based projections to help you decide which team will have the best season.