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Converting Playoff Odds to a Game Win Expectancy

It's going to get nerdy

A few days ago, in a game thread there was a discussion on how the current Royals playoff chances felt like being down by two runs with one inning to go. I got to thinking what would be the equivalent game winning percentage to a season's playoff chances, so created a somewhat simple table to find comparable playoff and game chances.

At every point in a game, the chances of a team winning can be known using historic data. For example, teams which are down two runs to start the 5th inning have historically come back to win the game 30.1% of the time. Basically, I wanted to match up the 5th inning to games played (works out 73 to 90 games played) and playoff odds to a similar game run/out state.

After several attempts, I created the following chart to match some game win expediencies (WE) to the playoff odds (embiggen).


  1. The WE data is for the Home team
  2. If there are no base/out state (ex. 12x), it is assumed to be the start of the inning (xxx).
  3. The colors match the same Run/Out states (ex. Dark Blue is always Up 4 with 0 Outs).

Don't feel over-whelmed, I will walk through it with the Royals right now. The Royals have played 123 games which would put them in the 7th inning (109 to 126 games). From, the Royals playoff odds are 14%. This value in the 7th innings is Down 3 with no outs. The Tigers playoff odds (96.6%), on the other hand, are the equivalent of being up 4 in the 7th.

While it won't save the world, it is an interesting chart to convert playoff odds to similar game situation.

Thanks to the book form of The Book for the Win Expectancy Tables