How To Create And Use NFL Power Ratings To Beat The Point Spread
Power Ratings are the crutch every bookmakers leans on.
I relied on mine each day for five years working for ASureWin as the Sportsbook Manager.
The majority of bettors do not use power ratings and have not experienced the clarity they provide. This is the case for two reasons.
Power ratings are a lot of work to maintain. They require constant updating and equal work spread across each team.
Power ratings are difficult to adjust. It is tough to make accurate movements each week and avoid making emotional, irrational decisions.
I do not expect you to watch every game. Life gets in the way and you do not have time for that. I do, however, want you to make the most educated bets possible.
I have taken my years of relying on power ratings and developed a simple method that you can use to create your own power ratings.
These ratings require no more than thirty minutes of “computer” work each week. With them you can create your own point spreads each week and compare to market prices to identify an edge.
Last year, my “top bets” using this method went 39–24–1 (62%) ATS. I will tell you how to identify top bets at the end of this article.
First here is a step by step guide to build and use these ratings.
Creating the Ratings
This method uses an end of season win total to produce weekly point spreads. I think you can judge how a team will finish the season more accurately than you can price teams each week.
Using math, you can cheat and create a point spread value each week based on your end point.
Think of these ratings like a road map. If you know where you need to get to, all you need to do it plot stops along the way.
Instead of evaluating all thirty two teams to create and end point, you can use the second most efficient NFL betting market as a guide.
Season win total markets have been open for three months and have been shaped by thousands of dollars. Aside from the Superbowl Winner, season win totals have more exposure to time and volume than any other NFL betting market.
To begin your ratings, sort the league by current 2017 win totals.
Those numbers are good on their own, but they can be made better.
Regression is a pesky thing. Markets tend to over and under react to results from the past season. To account for regression and to further strengthen the numbers, use the Pythagorean Differential from last season.
For those of you not familiar with the Pythagorean Differential, it is a famous statistic from sports that generates an expected win value based on points scored and allowed. This identifies luck and outliers and helps illustrate market bias.
For the ratings, take the opposite of the Pythagorean Differential for each team last season and plug it into the spread sheet.
The sum of the “2017 betting markets win total” and the “2016 pythagorean differential” will produce the “Power Ratings Win Total (P-R-W-T)”.
The PRWT will be the number that dictates everything for you during the season. This is the number that you adjust week to week and is a direct prediction of how you think each team will finish at the end of the season.
Using the Ratings
To generate point spreads each week, you must compare two teams playing each other and determine the difference in their “Power Ratings Win Total”.
For each half win of difference, you add one point to the spread.
The New England Patriots open the season against the Kansas City Chiefs.
The New England Patriots have a “PRWT” of 11.5 and The Kansas City Chiefs have a “PRWT” of 7.5.
If you subtract 7.5 from 11, you can determine a difference of four full wins.
You know that each half win equals one point, therefore, if the difference is four wins, that is eight half wins, or eight points. The Power Ratings Spread is New England -8.
You might be wondering why per each half win you apply one point of advantage.
The reason for this is simple. If two teams play each other and one team is favoured by three points, the typical moneyline price is -145 (1.69). Those odds equate to an implied win probability of 59%.
If over the course of a season, a team is favoured by three points on average, they would be expected to win 59% of their 16 games.
That equates to 9.5 wins.
League average is 8 wins. Three points better than league average is 9.5 wins or 1.5 wins better. Therefore, each half win is worth one point to the spread.
Determining the spread using the difference in PRWT is great, but, it can be better.
Travel time and venue change has a big impact on the outcome of NFL games and markets. To create an even more accurate price, you must account for home field advantage.
The general rule among bookmakers is that home field is worth three points. I however, have my range from 2.5 to 3.5 points. Here is my personal rating of each home field in the NFL and full ratings for this season.
New England has a home field rating of 3.5 points. Adding that to the week one game against Kansas City produced a Power Ratings Spread of New England -11.5, a difference and power ratings advantage of 3.5 points.
Adjusting The Ratings
Power ratings require care and attention. The more accurate you are, the more success you get in return.
It is important to remember that emotions and power ratings do not mix.
Rarely — if ever — will an NFL team do something in a single game that will be worth more than a half win adjustment.
An irrational adjustment can throw off the entire balance of your power ratings. If this is your first season relying on ratings, I encourage you to under adjust rather than over adjust.
Remember, you are guiding these teams to their end point to determine an edge, not trying to predict performance week to week.
Injuries spark emotion. Avoid instant adjustment on injuries at all costs. Unless it is a quarterback, centre or a handful of elite skill position players, the chances of the “PRWT” being affected by more than half a win is unlikely.
You would be better suited keeping an eye out for “cluster injuries”.
A cluster injury is when a team suffers multiple injuries at correlating positions. For example, multiple defensive backs, linemen or receivers. These are injuries which can devalue teams and affect “PRWT” a great deal.
As with any set of power ratings or prediction model, there will be outliers. It is difficult to have thirty two teams compute together. Outliers are easy to identify during the season and should be approached with caution.
The temptation can be there to over adjust these teams to make them “fit” in their place. Do not do this.
It is not unusual to see a couple teams dramatically over or under perform. Use this information to your advantage and spot situations where regression can occur. Do not force something to happen. It is a long season.
Identifying Top Bets
Last year on my website (www.adamchernoff.com), I established top bets as any advantage indicated by the ratings of three points or more. If you backed each of these bets; you would have gone 39–24–1 (62%) against the spread.
As always, if you have any questions or comments on what you just read, reach out to me on Twitter. I am available anytime during the day in my messages and am happy to chat or help out anyway I can.