One of the biggest misconceptions in NFL DFS is Vegas lines are the best predictor of who the top scoring defenses will be. It drives me nuts when I hear people say things like, “I am using this defense because their opponent has the lowest implied total.” I also hate when people say that a defense is a great play because the total of the game is low. This line of thinking does not jive with the way fantasy points are scored by your defense, and can lead you astray.
The league average for points scored per game was in the 21-27 point range, and so was the mean for teams in the league. Allowing 21-27 points in a game is worth a whopping zero fantasy points for your team defense. If the number is between 14 and 20, you get a one point bonus and you only lose one point if it comes in slightly higher, between 28 and 34. This is where most NFL games end up, and therefore most defenses are going to be in a range of 1 and -1 if you overweight the importance of the final score like most people do. Each NFL team plays sixteen games and we have thirty-two teams in the league. That means a total of 512 final scores in a season, and we only had two shutouts in 2015. Three of them in 2016. The ten point bonus for holding your opponent scoreless was only collected five times by a fantasy defense in the last two seasons. To take it a step further, the seven point bonus for limiting the damage between three and six points was only collected twenty-three times, or less than one and a half times per week in 2015. The number was a tad lower in 2016. With the median and average defensive fantasy scores per game both hanging around the mid seven point range, we can see that clearly the main component of a defensive fantasy score is outside the number of points they allow.
How to Predict Defensive Fantasy Scores
A better predictor of the fantasy score for a defense is the number of sacks, interceptions and fumbles they create. Defenses that create a lot of these fantasy point scoring opportunities are the ones that end up with the most points. By extension, they also are not allowing the opposition to score many points, so the bonus points from the scoreboard boost the floor of the defensive plays they make. The highest scoring defense of the week is not always the one who gave up the least amount of points, as we have seen teams give up 28+ points for a negative fantasy points allowed number and still wind up as the top fantasy defense on the week. This highlights the importance of the other stats and how foolish it is to concentrate solely on the potential for a low number of points allowed according to the Vegas totals.
This concept is easier to understand through the use of examples, so here are two different scenarios from 2015. In week two, the Green Bay Packers beat the Seattle Seahawks and held them to only 17 points. They had two sacks and one fumble recovery for the game. They scored a total of seven fantasy points for their effort. Seattle kept the ball on the ground a lot due to the putrid play of their offensive line early in the year in pass protection. Other than a very infrequent fumble, you can not rack up defensive fantasy points for sacks and interceptions when the opposing team is keeping the ball on the ground. The clock is also constantly moving, so the game tends to have less overall plays run, which gives you even less opportunities to create positive point scoring situations.
That same week, the Arizona Cardinals were able to pressure Jay Cutler of the Bears all day long. Well not all day, as he left the game and Jimmy Clausen played a large role too. The Cardinals were up big early, as they cruised to a 48-23 win. They actually gave up six more points on the day than Green Bay did, yet they were able to score twice as many fantasy points in the process. Despite giving up some garbage time points to get the Bears total up to 23, the Cardinals were able to record two sacks, two interceptions and two defensive touchdowns. When a team has a big lead, they force the opposition into becoming a one dimensional passing attack in order to catch up on the scoreboard. When a team is forced to drop back and pass more often, they are allowing a defense more opportunities to record sacks, get interceptions and even record the occasional strip sack fumble recovery for a TD. All of those positive point scoring opportunities for a defense happen more often when the team has a lead. The more a team passes, the more chances the defense has to make plays. Positive scoring plays that you can not get when a team is attacking you via the run. Despite giving up more points on the scoreboard, the Cardinals were far superior in terms of fantasy points scored.
I do not want people to get me wrong when I say Vegas lines are not important. They are important in helping us try to decipher the game flow. If a team is favored by eight and the total is only 46, then I do think the low 18 projected points for their opponent means something. When two run heavy teams have a total of 41 and the spread is less than 3, I’m staying away from using the defense who is slated to allow the same 18 points. The game is likely to stay closer with neither team being forced to pass much. We will see less plays and that translates into less opportunities to score fantasy points.
Hopefully these examples help you see the folly of your ways. If you are someone guilty of saying you want to play this defense because the total is low or the other team is not expected to score a ton of points, make sure you can back it up with a reason they will be forced to pass. If they struggle containing the pass rush too, that is the ideal situation we want to present potential fantasy upside for our defensive.