The KC Royals defied all logic to win the 2015 World Series. They won more games than any American League team after respected projection system PECOTA predicted 72 wins. They pulled off a record-setting seven multi-run comebacks during the playoffs, including three victories in which win probability systems estimated them to have a single digit percentage chance to win.
Now, backward-looking sabermetric measures are struggling to explain how the Kansas City Royals did it.
Wins Above Replacement (WAR) is a catch-all sabermetric stat used to provide a rough estimate of overall player value. Public baseball statistic sites Fangraphs.com and Baseball-reference.com publish WAR values (typically differentiated as fWAR and bWAR) for every player in baseball history, broken down by season, using slightly different algorithms. These two value systems have become the go-to measures for player value for most pundits and fans (many team analytic departments have their own WAR measures).
These systems have become so pervasive that they’re used by player agents in contract negotiations, and sportswriters to evaluate performance for post-season awards. They’ve obtained this position because of many studies that show a strong correlation between WAR and team success.
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Well, those correlations HAVE been pretty good until the KC Royals came along.
A “replacement level” team (a team composed of average AAA players) is projected to win roughly 46.74 games against major-league competition. You can add team WAR values to replacement level wins to get an estimate for wins a team “should” have achieved given the cumulative performance of their players.
In most cases, team WAR plus the replacement level wins should be pretty close to the team’s actual record—with some leeway for “variance” in run scoring or run prevention in critical (or high-leverage) situations. Analysts often attribute wildly divergent results to “luck”. In 2014, the Kansas City Royals earned a total of 38.5 fWAR as a team. This number suggested that the 2014 KC Royals actual production should have resulted in 86 wins.
That’s not a bad estimate when you consider the 2014 Kansas City Royals won 89 games, but 86-win teams aren’t supposed to come within one game of a title.
Fangraphs’ WAR system did an even worse job with the 2015 KC Royals. The 2015 World Series winner earned a very similar 38.3 fWAR during the regular season, broken down into 24.9 fWAR for position players and 13.4 fWAR for pitchers. Performance data suggests the Kansas City Royals “should” have again won 86 games. According to fWAR, the 2015 and 2014 KC teams were approximately equal in performance.
Yet, the 2015 KC Royals were markedly stronger than the 2014 team. They won 95 rather than 89 games, and cruised through September with a double-digit division lead. The 2015 Royals also enjoyed a +83 run differential compared to only +27 for the 2014 team.
[Note: the above two paragraphs were corrected from the original posted version after Jeff Zimmerman pointed out my error that the Royals only accumulated 30.3 fWAR]
Fangraphs also calculates CLUTCH, a metric designed to measure how well a team performs in critical situations that can cause them to win or lose a game. Fangraphs refers to these moments as “high leverage” situations.
Lo and behold, the 2015 Kansas City Royals were not only were the “clutchiest” team of 2015, they had the 4th best CLUTCH ranking of any major-league team going back to 1974.
That explains it, right? The 2015 KC Royals really weren’t all that talented, but they performed their best with the game on the line. In short, they were a team that knew how to win.
Except, there’s one little problem with this narrative. Sabermetric studies show that CLUTCH is not a metric that is repeatable by either individual players or teams. This fact suggests that “luck”, “fortune”, or “variance” is the explanation for CLUTCH rather than any kind of baseball skill. Some have suggested that the KC Royals unusually high contact rate is why they performed so well in high-leverage situations, but studies show little correlation between CLUTCH and team contact rate.
Sabermetrics would have you believe that the 2015 Kansas City Royals got really lucky over a 162-game season, then defied one in a thousand odds to pull seven improbable comebacks in the playoffs.
Or, maybe—just maybe—the 2015 KC Royals don’t fit in a sabermetric box.