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NFL Week 2 Elo Ratings And Playoff Odds

It’s a cliche: Every game counts in a league that plays just 16 of them. But Benjamin Morris’s findings in his debut Skeptical Football column were nevertheless striking: A Week 1 or Week 2 game can affect an NFL team’s chances of making the playoffs by as much as 20 or 30 percent.

We also see that reflected in FiveThirtyEight’s NFL Elo ratings playoff odds, a feature we debuted last week.

What are Elo ratings? The short version: Elo ratings are a simple mathematical system originally designed to rate chess players. They’ve since been adapted to a number of sports such as soccer, and we’ve adapted them to the NFL. The Elo ratings only account for fairly basic information like wins and losses, strength of schedule and margin of victory. There are more advanced systems out there, but Elo ratings are transparent, easy to calculate and we can do a lot of fun stuff with them, like simulating the rest of the season and calculating playoff odds. For more on the methodology, see here.

In our Week 1 ratings — which were based on a team’s Elo rating at the end of last season — the New England Patriots had a 73 percent chance of making the playoffs and the Miami Dolphins had just a 32 percent chance. But the Dolphins upset the Patriots, and now it’s almost even: New England is at 54 percent to make the playoffs and Miami at 50 percent.

Why such a big shift? Well, every game counts (especially a divisional game; our simulation accounts for playoff tiebreakers). But also, the Patriots now look slightly worse than Elo originally pegged them, and the Dolphins look slightly better. Before Week 1, Miami had projected to win 7.7 games; it now projects to win 9.1. In other words, one NFL win for the Dolphins was worth more than one win in the Elo standings because Miami’s Elo rating improved.

Here are the latest Elo ratings and playoff odds for all 32 teams: