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Strength of Schedule

Strength of schedule is one of the many factors that fantasy football players often include in their player rankings to try and get an edge over their opponents. One of the problems with it however is that there is so much parity in the NFL that a bad run defense can become one of the best ones in the following year. This article will consider statistics from the past five seasons in order to determine whether or not strength of schedule is one of the factors worth worrying about in fantasy football.

The first step for this analysis was to determine how much defensive statistics vary from year to year. In order to do this, I used the “points allowed by position” statistics which tell us how many fantasy points each team allowed to quarterbacks, running backs and wide receivers in a given season. The goal was to determine how much a team’s statistics from a given season impact that team’s statistics for the next season. Using statistics from 2003 through 2008, here are the formulas that predict the most accurately each team’s points allowed by position for the next season (it may seem complicated but just bare with me, I’ll explain what those mean in a second):

These formulas show us that it is very difficult to predict how defenses will perform in the upcoming season as only 20% to 30% of the previous year’s statistics help us predict next year’s statistics. For example, the Arizona Cardinals were the worst passing defense last season by allowing 339 fantasy points to opposing quarterbacks but according to the above formula you can expect them to allow only 288 in 2008 (212 + 0.224 x 339 = 288). For those who doubt these formulas here is an interesting statistic: of the ten defenses that allowed the most fantasy points to quarterbacks in 2007, only three remained in the bottom ten in 2008 and three were in the top ten.

The next step was to use these numbers and determine each team’s strength of schedule by position for the 2009 season. The following charts show the three easiest and the three hardest schedules for each position as well as the multiplier which shows how much easier or harder their schedule is compared to the league average:

These numbers show us that the difference is less than 5% between the teams with the easiest schedules and the teams with the hardest schedules. For example the Minnesota Vikings have the easiest schedule for running backs but we can expect the defenses they will face to allow only 2.4% more fantasy points to running backs than the league average. This means that if you project Adrian Peterson to have 300 fantasy points, his easier 2009 schedule would mean you can expect him to have 307 fantasy points. As you can see, it makes absolutely no sense to look at strength of schedule for 2009 based on last year’s defensive statistics as the difference is minimal. The Vikings have 12 of their 15 first games against teams that were below average in run defense in 2008 but who says those teams will be as bad in 2008?