Here’s the question all NFL fans ask somewhere around the middle of the season — especially those whose teams have a chance of making the postseason: “How difficult is the remaining schedule for my team?”
Or more specifically, “How difficult is the remaining schedule for the Kansas City Chiefs?”
Here’s how things stand going into Week 10:
Strength of Schedule (by W/L)
As you can see, the Chiefs have the 19th-easiest strength of schedule to finish the season. That’s pretty... average.
But I’d like to draw your attention to the final column of this table, which converts each team’s strength-of-schedule into standard deviations from average (sometimes this is called a Z-score) and displays it an easier-for-humans-to-grasp letter grade.
This tells us that the Chiefs actually do have an average schedule — but also that the teams ranked between 13th and 20th (also with C grades) all have strength-of-schedules that are not statistically different from each other. All of these C teams have measurably easier schedules than teams with C- grades — and measurably harder than teams with C+ grades.
But here’s an important point: the difference between these teams with measurably different C grades is not statistically significant.
Here’s the rule of thumb: for two values measured in this way, a statistically-significant difference exists only when they are at least a full letter-grade apart — for example, B to A or D+ to C+.
But hold up... wait a minute!
Is simply averaging the won/lost records of a team’s upcoming opponents really the right way to do this? Bill Parcells famously said that “you are what your record says you are” — and he had a point. But it’s also true that not all records are created equal; one team’s 6-2 record against a bunch of poor teams doesn’t say the same thing as a another team’s 6-2 record against a bunch of playoff contenders.
There are several methods of rating the relative strength of football teams that take the quality of their previous opponents into account. Using the simplest of these — the SRS system used by Pro-Football-Reference.com — let’s see how that changes the NFL’s strength-of-schedule going into Week 10.
Strength of Schedule (by SRS)
Whoa! The Chiefs drop from 19th-easiest to 29th-easiest. Once we’ve applied the simplest possible method to adjust for the quality of upcoming opponents, a number of teams move around. The Chiefs, Chicago Bears, New Orleans Saints and Tampa Bay Buccaneers all have harder schedules that we first thought, while the Houston Texans, Indianapolis Colts, New York Giants and San Francisco 49ers all have easier ones.
But again... let’s not get too excited. The letter grades tell a somewhat different story. Using SRS, the Chiefs fall just outside that average range with a D+. The Buccaneers — falling from 10th to 25th — come closest to dropping a full letter grade.
So using a different dataset to compare relative strength-of-schedules does make a measurable difference — although not necessarily a significant one.
There are other ways to measure team strength based on the quality of their previous opponents. The other big ones are the ELO ratings used by FiveThirtyEight.com and DVOA published by FootballOutsiders.com. Along with SRS, these systems all use different methods. While they all have pros and cons, they arrive at fairly similar (but certainly not identical) results. Here’s a side-by side comparison at how each of these systems now assess the strength-of-schedule for every NFL team:
Adjusted Strength of Schedule
The rank (and grade) for each system are shown in parentheses. As you can see, in most cases, they give fairly similar results — especially when you compare letter grades. Finally, I averaged the Z-scores for all three results to create the aggregate letter grade for each team — also displayed in parentheses.
So what have we learned?
One thing is that the Chiefs may have a somewhat harder remaining schedule than you may have thought. During a recent Chiefs game broadcast, the network displayed a graphic that said the team had one of the league’s easiest schedules. While that might have been true in that moment, game results since then (including a lot of recent upsets) have changed things — especially when you take the extra step of considering the real quality of upcoming opponents.
The other thing is that while teams like the Denver Broncos, Jacksonville Jaguars and Atlanta Falcons should be worried — and teams like the Baltimore Ravens, Seattle Seahawks, Cleveland Browns, Miami Dolphins and Green Bay Packers can let out a little breath — most other teams are in the average range. The Chiefs may fall on the harder side of that range, but they still have Patrick Mahomes, an even-better defense and a 17-1 record in the last calendar year.
Those things are likely to count for something.