Fantasy football is a difficult game that’s only getting tougher. Like poker, it’s a game comprising partly luck and partly skill. By playing as optimally as possible, we can always shrink the level of influence luck has on the game, but, still, the best player still won’t always win.

In order to succeed in fantasy football, we must try to maximize every potential edge, no matter how small. In today’s case, that means talking about an unpopular but important topic — how and when to draft a fantasy defense, and which defenses stand out this year.

Picking a defense

There’s a prevailing narrative among fantasy experts that team defense scoring is mostly random, with sacks, turnovers, and touchdowns making up the bulk of scoring, but being highly unstable and hard to predict year-over-year. So, I decided to dig into the numbers to see whether this was true.

How to draft a fantasy defense. Correlations of various stats to fantasy points and fantasy points in the following year. Conclusion: It's super random. pic.twitter.com/IfZBE86Wuj — Scott Barrett (@ScottBarrettDFB) April 20, 2018

Basically, the narrative holds true.

Sacks and turnovers (or, really, sacks plus turnovers) have the highest correlation to fantasy points for fantasy defenses, but they’re also highly unstable (read: random) metrics — sacks and turnovers fluctuate wildly among defenses year over year.

The data suggest you’re better off selecting a defense based on raw fantasy points in the year prior than any other stat we’re looking at, and even then, the correlations were exceedingly low. Though, it’s noteworthy that prior-season fantasy points scored fared much better than in-year ADP (0.03), suggesting you’re better off just drafting last season’s top-scoring defenses rather than going off ADP.

When to draft a defense

In my own leagues, I’m typically not even drafting a defense, unless I’m drafting very close to the start of the season. Instead, I’ll draft high-upside players in the last round like Chase Edmonds or Ty Montgomery. If Le’Veon Bell or David Johnson were to suffer an injury in the preseason, either one of these late-round players could be a weekly RB2 or better — a much greater advantage than owning a top team defense. If that happens, I’ll drop a different player and add a defense right before Week 1.

Of course, Bell and Johnson are far more likely to escape the preseason unscathed. So, I’ll probably end up dropping one of these players to add a defense right before the start of the season. For the remainder of the year, I’ll continue to stream defenses, picking units in favorable matchups (against poor offenses). If one of these defenses look like it could be an every-week starter, I’ll hold onto it.

Here’s why this works: Last season, the Texans ranked fourth among team defenses in fantasy points per game (7.8). However, they were outscored by the average of all defenses against Buffalo (8.8), Arizona (8.7), San Francisco (8.3), and Oakland (7.9).

What to look for when streaming

(Earlier this summer Daniel Kelley offered up strategies for streaming a defense in fantasy without knowing anything at all about football, a bare-bones approach that is still effective.)

The highest week-to-week correlations I found (to team defense fantasy scoring) were in passer rating and sacks per dropbacks. In-season passer rating (for offenses) and opposing passer rating (for defenses) both had a correlation of about 0.054. When we combine these two numbers, the correlation jumps to 0.102. In-season sack rate (for offenses) sits at 0.045 and (for defenses) 0.036 but jumps to 0.075 when combining both figures. All other numbers I looked at, including pressure rate and rushing efficiency were far less highly correlated.

We should also be targeting defenses that are heavily favored by Vegas and/or playing at home. Since 2014, teams favored by over a touchdown or more average 7.5 fantasy points per game on defense. Teams favored by double digits averaged 8.3 fantasy points per game over this stretch. On average, over this stretch, home defenses outscored road defenses by +0.9 fantasy points per game.

Beyond that, stick to intuition. Target defenses up against inexperienced or inefficient quarterbacks who are more sack-prone or turnover-prone than the league average rate.

Who to look for when streaming in 2019

If going the streaming route, I’d look at Philadelphia (ADP DST12), favored by 8.5 points at home against Washington in Week 1. Cleveland (DST7) and Dallas (DST9) also stand out as being heavy home favorites in favorable matchups but have a higher ADP. If you’re really forced to scrape the bottom of the barrel, turn to the Jets (DST23), favored at home against a Bills team that gave up the most fantasy points per game to opposing defenses last season.

Who to draft in 2019

Okay, still not sold on my preferred streaming approach? That’s fine, though I’ll still encourage you to wait until the very end of your draft to select a defense. Here are some of the defenses I’d look to target in 2019:

On paper, the Bills' defense (DST18) looks stacked, with six starting defenders grading 75.0 or better last year, not including rookie Ed Oliver (our second-highest-graded defensive tackle in college last year) or Tre'Davious White (our sixth-highest-graded cornerback in 2017). Their offense might not be doing them many favors this year (in terms of gamescript and favorable field position), but they do get to play the Dolphins and Jets twice each, and they start off the season in favorable matchups against the Jets, Giants, and Bengals.

Outside of Buffalo, I’d be looking to do what the data suggest we do — target defenses who were more productive last year than their ADP implies and/or are likely to rank highly in point differential. The Patriots lead the league in Vegas projected win total (11.0), followed by the Rams (10.5), Saints (10.5), Chiefs (10.0), Colts (9.5), Browns (9.5), Chargers (9.5), and Bears (9.5). Of these teams, the Browns (DST9), Saints (DST10), Patriots (DST11), Colts (DST12), and Chiefs (DST13) are most attractive by ADP.

The Browns and Saints would be my preferred targets, ranking third and sixth, respectively, in our 2019 pass rush rankings. The Chiefs deserve some credit for consistency, ranking top-three in fantasy points per game in three of their past five seasons, and top-12 in four of their past five seasons. Their defense isn’t great on paper (though they should be better than last year), but having Patrick Mahomes under center should lead to plenty of blowouts, which should help defensive scoring.