Around the time the days begin to get shorter and stores deck out in red, white, and blue, baseball fans and analysts may start to compare lots and lots of numbers. Player OPS, wRC+, ERA, all of the RBI, home run, and stolen base counting stats. Soon, the league will showcase the most professional of professional baseball players in Seattle. In the spirit of the times, then, why not compare important ball club stats? Who truly are the best teams today?
One such stat sticks out in this quest, and it is today’s focus. Run differential is often believed to be a candid means of assessing a team’s true talent. Score significantly more runs than the opponent, and you are likely to win games.
The Minnesota Twins are rolling through midsummer with a just-good-enough 40-39 record. FiveThirtyEight’s preseason predictions said the Twins would finish 85-77, so things have gone mostly according to plan. That is reflected in Minnesota’s +34 run differential. They have scored 340 runs in the first 79 games without much help from their stars (yet). However, their defense has only allowed 306 runs. Therefore, the Twins should be winning games. But how many wins should they have?
A quick gander at the rest of the standings shows a compelling story. The Baltimore Orioles, New Yankees, Toronto Blue Jays, and Boston Red Sox have run differentials ranging between +26 and +21. In contrast, the Cleveland Guardians are in second place in the AL Central and have a dramatically worse -20 run differential. The NL East’s Miami Marlins and Philadelphia Phillies have defied all odds with their -15 and -16 run differentials, respectively. The Marlins have a .570 winning percentage, third-best in the NL. And the Phillies are eking out a 40-37 record despite their run differential woes. To level-set, what are these teams’ records supposed to look like based on their run outputs?
The answer can be found using a modified equation of Bill James, coined Pythagorean Expectation. The actual formula is rooted in standard deviation. Every team has good and bad days, but those that simply score more runs than they give up are expected to win more games when they perform poorly and lose fewer games when they perform well. In my opinion, the only truly important aspect of this sort of thinking is that it assumes a two-run homer up 8-0 in the 7th inning requires just as much skill as one down 4-2 in the 4th inning. Every pitch of every game is thrown with the same conviction and will to win as any other. There are a few exceptions, but it rings mostly true.
What does this formula I speak of look like? One DIVIDED by one PLUS (runs allowed DIVIDED by runs scored) squared. Because that is horribly impractical to read, here it is in a much easier format:
The resulting number is the “win ratio.” Multiply that number by games played, and you’ve got the number of expected wins.
The fun part is finally here (or perhaps the not-so-fun part). The Twins should be 43-36. That’s only three more wins than they have. Surely, we can cause even greater disappointment and anguish on the never ending Minnesota fan’s journey of self-deprecation. In fact, we can.
Base Runs are yet another statistic that can be used to determine expected win percentage. The formula uses somewhat similar ideas that were seen when looking at optimizing a lineup. The number of runs a team can expect to score is based here on the number of singles, doubles, triples, etc., a team hits. Surely the Twins and their dissatisfying run production won’t reflect well in expected winning percentage utilizing Base Runs, right? Actually, the Twins should be 45-34 based on how well their offense has hit. Clutch hitting is and will remain important.
As the season carries on, Minnesota will naturally have ups and downs. From high-paid bats disappointing to season-ending injuries, there’s already been a host of frustrating headlines. While it may not always feel like it, the Twins are a better team than their record indicates.
