At the start of this season I decided to put every NFL game into a spreadsheet, update it weekly with scores, and have some fun playing with the numbers (I'm a nerd). Around week 3 I veered away from just tracking the common numbers and started creating a Power Ranking system. Power rankings are an endless topic of debate, especially when the rankings are arbitrarily decided by the eye test. I wanted to come up with a method that relies only on the numbers.
What makes one football team better than another? There are all kinds of stats that try to quantify this, most of us here are partial to DVOA while others have differing opinions (total yards, century old rings, etc.). When it really comes down to it, how do you win a game? You score more than your opponent. Pretty simple stuff, right? But, when it comes to ranking teams, not all points are equal. Dropping 30 on the Jaguars isn't much of an accomplishment (the Jags have allowed 30+ in 4 out of 5 games this season) but putting up 30 against the Seahawks is impressive (the Hawks have only allowed 30+ three times since the start of the 2012 season).
I decided to take every game a team has played and compare their points scored with the opponents average points allowed. Likewise with the team's points allowed and the opponents average points scored. Totaling these for the season gives us Points For Differential (PFD) which indicates how many points a team scores above their opponents average allowed (positive is good, negative is bad) and Points Allowed Differential (PAD) which shows how many points a team allows above their opponents average points for (negative is good, positive is bad). These can be combined (PFD - PAD to preserve good and
evil bad) to create Opponent Adjusted Point Differential (OAPD). OAPD represents the overall point spread above the opponent's average score. The higher the number, the more a team dominates their opponents.
Enough Reading, Get to the Numbers!
Seattle currently sits in first, thanks to the #2 offense and #4 defense. This is a very balanced, very good team. Denver is 2nd overall, ranking #1 in offense and #10 in defense. After these two there is a significant dropoff before the next tier, containing San Diego (#8 offense, #2 defense), and Baltimore (#16 offense, #1 defense).
This is where teams stand in OAPD through week 5
|Team||W||L||PFD||PF Rank||PAD||PA Rank||OAPD|
|3||San Diego Chargers||4||1||2.75||8||-6.88||2||9.63|
|8||New York Giants||3||2||4.50||4||-0.74||14||5.24|
|10||Green Bay Packers||3||2||4.13||7||-0.10||16||4.23|
|11||Kansas City Chiefs||2||3||0.52||17||-3.24||11||3.76|
|13||San Francisco 49ers||3||2||-0.58||20||-4.14||9||3.56|
|17||New England Patriots||3||2||1.72||13||0.40||17||1.32|
|21||New Orleans Saints||2||3||0.03||18||3.45||23||-3.42|
|28||New York Jets||1||4||-4.51||28||3.57||24||-8.08|
|29||St. Louis Rams||1||3||-4.35||27||5.00||29||-9.35|
|30||Tampa Bay Buccaneers||1||4||-5.83||30||6.96||31||-12.79|
Overall I think this list aligns well with my perception of teams (not that my opinion is very meaningful). The ratings are still going to fluctuate significantly as we progress through the season and score outliers are lessened by the number of games.
- OAPD isn't fooled by the weak schedules of the Cowboys and the Eagles who, despite 4-1 records, rank 14th and 16th respectively.
- Kansas City is ranked 11, the highest ranking team with a losing record
- Pittsburgh is ranked 24, the lowest ranking team with a winning record
- Atlanta's #3 ranked offense is balanced out by their #28 ranked defense, resulting in the closest to neutral OAPD rating at 0.05
- Jacksonville is ranked dead last in defense and overall, but are saved from the clean sweep by their 31st ranked offense (Oakland is #32)
When I first compiled this info back in week 3 I was skeptical about a lot of the rankings. To reassure myself that this wasn't a terrible idea I went back through the entire 2013 regular season to calculate PFD, PAD, and OAPD.
|Team||PFD||PFD Rank||PAD||PAD Rank||OAPD|
- Denver and Seattle are once again the top 2 teams by a wide margin.
- 11 out of the top 12 teams by OAPD made the playoffs
- Arizona is the lone non-playoff team in the top 12 and they were widely considered the best team to miss the postseason
- Green Bay, the remaining playoff team, finished ranked #19
- Denver, New England, New Orleans, Seattle, and San Fran were the top 5 offenses
- Seattle, Carolina, San Fran, Kansas City, and New Orleans were the top 5 defenses
Wrapping Things Up
Based on the 2013 results OAPD appears to be a pretty reliable method to determine team rankings. No method is perfect, and I'm sure plenty of you will find flaws in this system, I welcome your criticism and I will try to incorporate your ideas to help improve future results. I am happy to continue these throughout the season if you find them interesting/helpful. I will also try to get them out earlier in the week so they don't get swallowed up by the next slate of games. Please let me know what you think!