Historical and Current Season Strength of Schedule (SoS)

The table above shows current NFL strength of schedule rankings, and can be filtered to include historical data going back to 2003. nfelo's strength of schedule rankings are based on Win Total Rankings at the start of the seasons, and then layer in actual results to get a more accurate picture of a team's true strength of schedule played to date, and strength of schedule remaining.

Understanding NFL Strength of Schedule (SoS)

What is Strength of Schedule?

Strength of schedule simply measures how good or bad an NFL team's opponents are relative to the rest of the league. Strength of schedule can be thought of in three different ways:

• Projected: How easy or difficult an NFL team's opponents were expected to be based on pre-season rankings.
• Played: How difficult an NFL team's opponents actually were to date.
• Remaining: How difficult an NFL team's remaining opponents are expected to be.

In the NFL, strength of schedule can play a major role in determining a team's win loss record, and, ultimately, their playoff chances. Material differences in schedule difficult are why the NFL often sees lopsided matchups in early rounds of the playoffs, as weak teams with easy schedules or divisions sneak past better teams that accumulated losses to quality opponents.

Let's take a look at why NFL schedules can differ so much in opponent quality.

How NFL Schedules Are Structured

The NFL creates schedules using a universal framework to ensure competitive balance. Each team faces:

• Six games against division opponents (three teams, played twice each)
• Four games from a different division within their conference
• Four games from a division outside their conference
• Two games from remaining divisions in their conference
• One additional out-of-conference matchup

Divisional and conference matchups rotate every year, which does help schedules stay balanced on a multi-year basis. However, this structure does create opportunity for major divergences within a season.

The divisional and conference rotation is fixed, meaning there is no balancing of schedule based on expected team quality. One division may get lucky and matchup against two relative weak divisions, while another may end up facing two great divisions.

These differences can amount to nearly a 4 point per game difference between the NFL's easiest schedule and the NFL's hardest schedule in a given season, which is why they have such a large impact on a team win loss records.

Traditional vs. Advanced SOS Calculations

While there is no ambiguity in who a team plays, strength of schedule calculations can vary significantly depending on the sophistication of the approach used.

Previous Season Win Percentage Method

The most common approach looks at upcoming opponents' combined winning percentage from the previous season. While directional, this method ignores year-over-year team changes and roster improvements, and it ignores the fact that not all wins are created equal.

A team that lost a lot of games because their QB went down with an injury will be significantly underrated, while a team that won a lot of "coin flip" one score games may be significantly overrated.

Previous Season Point Differential Method

The win percentage method can be improved by looking at the previous season's point differential instead, which is a much more predictive measure of a team's underlying ability. However, this method is still backward looking, making it fairly inacurate overall.

Win Total Projections Method

To make opponent quality forward-looking, some analysts use projected win totals instead of previous season data. Since this measure is more relevant to the upcoming season, it does offer a more accurate projection of opponent quality.

However, projected win totals are still dependent on a team's schedule. Teams with easy schedules will have higher projected win totals than their underlying quality would otherwise indicate. To use win totals effectively, you need to also adjust recursively for the effect the schedule itself.

Win Total Rankings - The Most Accurate Method

To measure predicted opponent quality, nfelo uses a custom model called "Win Total Rankings" that solves the key limitations of other methods:

• Win Total Based: Uses win totals as a baseline forward-looking measure of a team's quality
• Price-Adjusted Accuracy: Adjusts the nominal win total value for the prices being charged on the over and under. For instance, if a team is projected to win 8.5 games, but the over is heavily juiced (ie -180), the true line is much closer to 9 than it is to 8.
• Schedule Circularity: Solves the recursive nature of win totals using a solver that identifies the implied team rating that most closely matches the projected win total when mapped out over the real NFL schedule.

Using this methodology results in significantly more accurate projections of opponent quality, which in turn results in more accurate strength of schedule rankings:

As seen in the chart, Win Total Rankings significantly outperform not only traditional methods like point differential and simple win totals, but also more advanced ranking models like 538 and DVOA.

Frequently Asked Questions

How is NFL strength of schedule calculated?

NFL strength of schedule is calculated by averaging the quality/strength ratings of all opponents a team faces. nfelo uses Win Total Rankings, which are derived from price-adjusted betting market win totals optimized through schedule analysis, but any method for defining team strength (ie - point differential, DVOA, etc) can be used.

Does strength of schedule change during the season?

Yes, remaining strength of schedule updates weekly as team performance provides new information about opponent quality. A team projected as strong in preseason may prove weaker, affecting their played schedule in retrospect and the expected strength of their remaining schedule.

What's the difference between strength of schedule and strength of victory?

Strength of schedule measures opponent quality regardless of game results. Strength of victory only considers the quality of teams you've actually beaten, making it a tiebreaker metric rather than a predictive or analytical tool.

Who has the easiest and hardest schedules in the NFL?

The table above shows exactly that! You can click each column to sort, meaning you can see who was expected to have the easiest or hardest schedule vs who actually did based on what we know about teams after they've played several games.

How does strength of schedule affect playoff chances?

Generally, teams with easier schedules have a meaningfully higher probability of making the playoffs. One important thing to note is that opponent quality is not consistent throughout the season. A team that has played a hard schedule so far may have a poor win loss record, but an easy remaining schedule, meaning their playoff odds are higher than their record would lead you to believe.