Live playoff probabilities are back. I’m breaking my resolution to only work on the ‘useful to teams’ subset of the football analytics Venn diagram because this was such a fun project last year. If you recall, AFA featured live updates for each teams’ chances of making the playoffs and advancing through each round, all the way to the Super Bowl. Fans of MIA, PIT and BAL might remember (and rue) this graph of the moment-by-moment chances their teams would win the last AFC wildcard slot in week 17. SD defied all odds and snagged it.

The playoff probabilities are updated as the games progress based on our live win probability estimates. Future game outcomes are based on the relative team strength and home field advantage. Each team’s chances of ending up in each possible seed is determined by playing out the remainder of the season in a simulation, repeated several thousand times. The proportion of times in the simulation that a team lands in each seed becomes the estimated probability of that outcome. This is often called a Monte Carlo simulation model.

The simulation also plays out the playoffs and Super Bowl for each season replication based on seeding rules, so byes and home field advantage are incorporated.

I’m not 100% confident that the tiebreaking rules are perfect. I think I’ve got them to at least 99%, but there may be some very obscure combinations of outcomes that aren’t handled properly in the simulation. For example, if three teams from the same division finish with identical records, and the one with the 3rd best conference record happens to have the best division record, the sim won’t handle it.

NFL tiebreaking rules are amazingly complicated. If you think they’re complex after reading them all, try explicitly programming them in code. I’d rather not reinvent the wheel. I consider the java-based simulator at NFL-forecast.com to be the gold standard, but it’s a Java app, and I can’t incorporate it’s model in a web-based format. So I had to do my own.

Of course, this kind of thing is the most fun on Sundays with lots of simultaneous games. I tried hard to get it ready yesterday but fell short. But we'll have it for tonight and the last two weeks of the season.

You can find the Live Playoff Probabilities page here, or under the Tools menu.