World Series Odds Using wRD

by: Matthew de Marte – October 2nd, 2018

Throughout the season, we have posted Power Rankings based off of wRD Win %. One of the reasons I created this rankings system was to see if it did a better job at predicting future performance than Pythagorean Win % and Regular Win %. Similar to the relationship FIP has with future ERA, I wanted to see if I could create an algorithm using a mix of Home/Road splits, run differential and strength of schedule combined to create something with superior predictive capabilities. While in yesterday’s post we tested the predictive power of wRD Win %, using first half results to predict the second half, there can be additional applications of this formula. Standard win % for teams are used to calculate odds regarding a team’s chances to win the World Series. While I cannot use wRD Win % while accounting for variables such as the days lineup and pitching match-up, it can be used to calculate postseason odds, such as the process described in this article written by Fangraphs Craig Edwards.

The process is pretty simple. First, I split each series and use a teams wRD Win % for home and away games. Then I use those numbers to calculate a teams odds of winning a home and away game. The table would look something like this:

Team Home wRD Win % Away wRD Win % Odds Home Win Odds Away Win
BOS 0.620903 0.6013741 0.521073944 0.525594187
NYY 0.542805 0.5706806 0.474405813 0.478926056

With each team’s odds to win each game calculated, I can go ahead and calculate a team’s chances to win the series in X amount of games. Below is an example of what those calculations look like. Note, since I have chosen the Yankees and Red Sox as the example, the calculations displayed are for a best of 5 series:

Team Odds W in 3 Odds W in 4 Odds W in 5 Odds Series W
Bos 0.142708 0.205581 0.194555 0.542844378
NYY 0.108815 0.169523 0.178818 0.457155622

The results would be red as: using wRD Win %, the Boston Red Sox have a 54.3% chance of defeating the Yankees in the ALDS. Of course, there is another potential opponent the Red Sox can face in the ALDS. There is a strong possibility they can face the Oakland Athletics in the ALDS as well. To calculate the Red Sox chances of advancing to the ALCS, I do the following:

(Odds A’s Win WC Game * Odds Red Sox Defeat As)+(Odds Yankees Win WC Game * Odds Red Sox Yankees)

The answer to the equation above are the odds the Red Sox advance to the ALCS. It is important to outline this process. The same calculations are used for every series and subsequent round eventually leading to each teams odds to win the World Series. If anyone is confused by this, feel free to reach out to the email provided at the end of the article. It is now time to actually see which teams have the highest odds of winning the World Series according to wRD Win %!

AL Team ALDS ALCS World Series Win World Series
HOU 59.5 % 33.4 % 19.5 %
BOS 52.3 % 26.0 % 14.2 %
CLE 40.5 % 18.0 % 8.6 %
OAK 50.4 % 23.9 % 11.3 % 5.8 %
NYY 49.6 % 23.8 % 11.4 % 5.9 %


NL Team NLDS NLCS World Series Win World Series
MIL 52.4 % 25.0 % 11.2 %
LAD 55.1 % 31.0 % 15.7 %
ATL 44.9 % 22.1 % 9.7 %
CHC 53.5 % 26.6 % 12.8 % 5.8 %
COL 46.5 % 21.0 % 9.1 % 3.6 %

Not to anyone’s surprise, the Houston Astros are the World Series favorite with a 19.5% chance to win the World Series. There are a few things to note here. The first is that the 92-win Dodgers have higher World Series odds than the 108-win Red Sox. I know the Dodgers topped the Red Sox in the final power rankings, but that is not the driving force behind these odds. The Dodgers have higher odds not because if they get to the World Series they have a better chance of winning it, but they have a much better chance of getting to the World Series than the Red Sox do, mainly because it is impossible for them to play the Houston Astros in the championship series. In 59.5 % of the realities the Boston Red Sox reach the ALCS, the big bad Astros will be their opponent, hence lowering their WS odds. Similar to that, three Wild Card teams; the Yankees, A’s, and Cubs all won 95+ games, with the Yankees winning 100. Yet, all three teams have identical WS odds around 5.8 %. This is not because they are that inferior to their competition. These odds are so low, because playing in the dreaded Wild Card Game, automatically cuts their World Series odds in half. That means that roughly 50% of all of their seasons end after the Wild Card game. These tough odds automatically slice any odds of winning the World Series drastically, no matter how dominate their regular season performance was.

There are your World Series odds based on wRD Win %! Just remember, the postseason is a giant crap-shoot, and these odds reflect that. Even the historically good Red Sox and Astros do not have odds that even crack 20 %. This reflects the randomness of the short sample size postseason baseball is played in and the difficulty to continuously succeed in such series. With that being said, of course there will be one team in the end that triumphs. Just because a team has low odds or high odds, once the first pitch is thrown every team has a chance, and that’s all we really care about as fans of this beautiful game. Tonight, another chapter in baseball history begins, if it did not already for most people during game 163. I hope you all enjoyed this piece, and if anyone is interested in the spreadsheet used, please reach out to ! The best time of year is here, may the best team (or luckiest) win!

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