Last year, the San Francisco Giants finished with the best record in the Cactus League (Arizona spring training) and the Tampa Bay Rays “won” the Grapefruit League (Florida spring training).
Some will say that those performances helped set up their regular season in which both teams won their division. The Giants went on to win the World Series.
But how much of a relationship is there between how well a team performs in Spring Training and how many games they win during the regular season? Turns out not much at all. In fact, there is almost no correlation at all.
Below we have a chart that compares the Spring Training and regular season winning percentages of every team over the last eight seasons (data via ESPN.com). If teams won games during the regular season at a similar rate as spring training, we would see all the dots clustered near a line that moved diagonally from the lower-left to the upper-right. Instead, we see the dots are spread out and the “trendline” is nearly flat.
We can calculate the level of correlation using R-squared. Think of it as a scale from 0 to 100, where 100 means you can predict exactly what a team’s regular season would be based on their Spring record, and 0 means no correlation at all. This chart has an R-squared of 6. In other words, there is almost no relation whatsoever.
The 30 MLB teams have played 240 seasons over the last eight years. Of those, 163 (67.9%) had a regular season winning percentage that differed from Spring Training by at least 100 points. For a perspective, 100 percentage points over the course of 162 games is the difference between finishing .500 (81-81) and winning 98 games (.605).
Almost one out of every five teams (18.3%) finished with a regular season record that was at least 200 points different than their Spring record. Over 162 games, 200 percentage points is the difference between winning 98 games and winning 64 games. In other words, one-fifth of the teams played like a playoff team in the spring and then lost nearly 100 games during the regular season (or vice-versa).
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