Friday, October 21, 2022
Revenge of the Defense
There is a very simple way to determine how much the offense and how much the defense influences the game. This applies not only to baseball, but to hockey, basketball, football, soccer, and any team sport you can think of. What we care about is the spread in scoring by the offense, and the spread in scoring allowed by the defense, on a team by team basis. If for example defense didn't matter at all, then the spread would be explained purely by random variation. And so the spread in offense would overwhelm the spread in defense. Similarly, if scoring was all about defense (run prevention), then we'd see a huge spread in runs allowed among the teams, and very little spread in run scoring.
Now, what do we actually see in baseball? Well, from 1974 to 2013, the spread in runs scored by 27 outs was one standard deviation of 0.46 runs, while for runs allowed it was 0.48 runs. So, we have slightly more spread in defense, but not that much more. This probably due to the fact that defense is about pitching and fielding, so you have two distributions coming together. I would imagine if I did this in hockey, where we have skaters and goalies, that the spread in goals allowed would be larger than goals scored. (Taking a guess for football, where the QB is so prominent, I'd guess the reverse. I won't even guess for basketball.)
But, since 2014, things have taken a much much larger turn. One standard deviation for run scoring is 0.44, so a bit tighter than we're used to. Runs allowed however has ballooned to one standard deviation of 0.56 runs. Why would that be? Well, in addition to pitchers and fielders being involved as two distributions, we also have a third distribution: fielding alignments. This is making it so that its a differentiator.
The 2022 season is a good example. The two highest scoring teams were the Dodgers and Yankees at 4.98 runs per game and above. We had FIVE teams allowing that many runs or more. The Tigers scored 3.44 runs per game, while we had two teams (Astros, Dodgers) who allowed far less than that. As a result, the spread in offense is tighter than the spread in defense. And so the determination of who will win the game will be more influenced by the defense than the offense.
Here is the year by year chart (click to embiggen) in the spread in scoring by offense and defense, where you can see the clear separation happening in 2014, not coincidentally when Shifts Attacked.
We can also show this as a percentage, taking the spread of defense divided by the spread of defense + spread of offense. From 1974 to 1983, it was 48% for defense. From 1984 to 2013, it was 52% for defense. Since 2014, that's exploded to 56%. Now, is it really about the shift and front office influenced fielding alignments? I don't know yet. It could also be about the shift in starting and relief pitching usage. I don't know yet. The next step is to look at the spread in talent at the player level.
What it could also be is how teams acquire talent. It could be that the spread in talent on the offense and defense side is the same year to year, but the way that talent is collected, there's more discrepancy or deviation on the defense side. This gets a bit complicated because position players contribute on both the offense and defense side.
Anyway, I'll look into it next time. And it'll be very interesting to see the results in 2023, when Infield Shifts are a thing of the past. That will more definitively give us the answer we're looking for. We can wait to see how that plays out too.
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