Week 10 MLS Power Rankings and OPI introduction

After a long break, our MLS Power Rankings are back and better than ever. During the offseason, we revamped our model to give a more accurate look at how teams around the league are actually performing. We’re calling this model the “Overall Performance Index”.

Overall Performance Index (OPI)

Yeah, the name is a bit pretentious, but “Power Rankings” is boring. This new model includes the same factors as the prior edition (points per game, strength of schedule, goal difference and expected goal difference), while adding several other factors to give a more rounded picture. Here’s how it works:

1. Points per game – 29%

Results are always the most important factor and have the biggest impact on a a team’s OPI.

This also only includes MLS results. Not Concacaf Champions League. Not US Open Cup. I’m sorry, I don’t make the rules.

2. Goal difference – 16%

This one is also fairly simple. How many goals a team allows versus how many they score is a pretty reliable indicator of how good a team actually is.

3. Form – 15%

One of the primary issues with the prior model was that games at the start of the year impacted their current standings just as much as recent matches. It was somewhat redundant, given how heavily weighted points per game are. In the new OPI, points per game over a team’s last five matches are also included, giving a more current view of performance.

4. Expected goal difference – 13%

If you know me, you know how much I love expected goals. While they’re interesting to look at for single match results, they also become predictive with over a larger sample size. They also bring an element of luck to the power rankings; a team may be creating plenty of chances and failing to finish them. This team will be scored higher than a team who doesn’t create or finish.

5. Strength of schedule – 12%

This carries over from the prior model, and is pretty simple. A 4-0 win over a bad team is worth less than a 1-0 win over a good team. Similarly, losing to a bad team will hurt a score much more than losing to a good team.

6. Home and away form – 12%

Another shortcoming of last year’s model was that it was blind to location. 6% of a team’s OPI comes from their home points per game compared to a 10 year league average, with another 6% coming from the road.

This is also why I haven’t published the rankings until now. Nashville SC started the season with an eight match road trip, and needed at least two home matches for their home form score to be realistic. They’ve still played significantly less at home than the rest of the league, and their score won’t normalize for another couple weeks, but it’s a start.

7. Goals Added – 3%

Goals Added (also known as G+) is a metric created by American Soccer Analysis that essentially measures how every action on the field increases or decreases a team’s chances of scoring a goal. This is yet another data point to help measure how a team is actually performing.

You’re probably bored by all this. I get it. Here’s the first edition of the Power Rankings using the new OPI model.

I’ll include more information on individual scores and changes in rankings in subsequent weeks. For now, I’m going to turn off twitter notifications.

Author: Ben Wrightis the Director of Soccer Content and a Senior MLS Contributor for Broadway Sports covering Nashville SC and the US National Team. Previously Ben was the editor and a founder of Speedway Soccer, where he has covered Nashville SC and their time in USL before journeying to Major League Soccer since 2018. Raised in Louisville, KY Ben grew up playing before a knee injury ended his competitive career. When he is not talking soccer he is probably producing music, drinking coffee or hanging out with his wife and kids. Mastodon

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