Back to the Future: Looking at Past Winners to Predict 2021’s Champions

As the 2021 MLB season winds down to its final weeks, the teams that can take home the Commissioner’s Trophy are narrowing, and four clear favorites have emerged from the chaos: the Giants, Dodgers, Rays and Brewers. Today, I’ll be looking at the past, and how predictable the World Series winners of the last twenty years were.

For this short study, I’ll be using OPS+ and ERA+, two statistics that–you might have noticed—end in the plus sign. What does this plus mean? It means that the two statistics are set so that 100 is league average; anything above it is above-average, and vice versa. So, with the plus, players (and teams) can be compared from different years…exactly what I plan to do today.

OPS stands for On-Base Plus Slugging Percentage; if you want more information on OPS, click this link: https://library.fangraphs.com/offense/ops/

ERA stands for Earned Run Average, which is the amount of earned runs a pitcher lets up every nine innings.

Yes, yes, you may argue that these two statistics are overly simple and do not represent a team’s true talent. You may be partially right—there are much better stats such as wOBA or SIERA—but for the purpose of this study, the easier-to-understand statistics will suffice.

So I looked at the World Series winners from 2000 onwards, and tallied each team’s OPS+ and ERA+.  The results are below:

AA Points is Above Average points, which is Team OPS+ added to Team ERA+. “Strength” is Team OPS+ minus Team ERA+.

The higher the AA Points, the more above average a team is (in terms of OPS and ERA). If strength is negative, the team is pitching-heavy. If strength is positive, the team is hitting-heavy.

There’s a lot that this table addresses, but I’ll go into a few important points that stood out to me.

1. World Series winners are typically better at pitching than hitting. Only seven out of the twenty-one teams had a positive strength (and one of the hitting-heavy teams were the 2017 Astros, with a whopping OPS+ of 123, because, well, you know why).

2. The 2020 Dodgers, if they played as well in 162 games as they did in the 60-game shortened season, would be one of the best teams ever, with 263 AA Points, more than 25 points better than the next best team (2016 Cubs). A team ERA+ of 143 (meaning that their team earned run average was forty three percent better than league average) is absolutely absurd.

3. There is a moderate amount of luck in winning the championship. The 2014 Giants were incredibly fortunate, as they were exactly league average in OPS and below league average in ERA. This was shown in their actual win-loss record (88-74) and their expected win-loss record (87-75), according to the Pythagorean Theorem of Baseball by Bill James. The 2006 Cardinals were even worse: They ranked below league average in the pitching and hitting departments.

In conclusion, it is common for a team with excellent pitching and above-average hitting to take the final prize. Teams that overpower in both respects (the 2020 Dodgers, 2018 Red Sox, 2016 Cubs, 2007 Red Sox) win the Series more often than teams with a bit of luck on their side, such as the 2006 Cardinals.

From the patterns of the first table, the four teams are neck-and-neck. The Rays are the only team with a better offense than defense, and the Brewers interestingly have an offense with an OPS 8% worse than league average, a surprising number for such a successful team. The Dodgers’ pitching puts them at a slight advantage, but as I said before, luck plays a significant role.

Thanks for reading, let me know who you think wins this year’s World Series in the comment section below!