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Dewan on value of defense relative to offense

John Dewan, author of the Fielding Bible, has a stat-of-the-week newsletter. This week he had an epiphany on the relative value of preventing and scoring runs.
The most significant discovery of my career

March 12, 2009

About two weeks ago The Fielding Bible—Volume II went to print. Since then, as I've been studying some of the data in the book preparing for interviews, I came upon a discovery that was truly amazing to me. The most amazing, and significant, discovery of my 25 years in the baseball analysis business.

The key mission of the second volume of The Fielding Bible was to translate all of our new defensive methods into one common number that would be understandable by everyone. That number is Defensive Runs Saved. How many runs does a player save for his team defensively?

We look at each player individually. We then do a team summary by adding up all the individual players. How many runs does an above-average defense save compared to an average team? The team with the best defense in baseball in 2008 was the World Champion Philadelphia Phillies. By combining all of our defensive methods, eight different methods across the nine positions in baseball, we estimate that the Phillies defense saved 78 runs. Using the rule of thumb that 10 runs is equivalent to one win, that's eight wins. With an average defense, the Phillies wouldn't have had even a sniff of the playoffs.

The worst defensive team in baseball in 2008? The Kansas City Royals. Their defense cost them about 48 runs relative to the average team. Comparing the Phillies and the Royals, the difference between the best and worst defensive teams in baseball was about 130 runs.

Now, remember that number. 130.

The best run-scoring team in baseball was the Texas Rangers with 901 runs in 2008. The San Diego Padres were the worst with 637 runs. That's a difference of about 260 runs.

Here's the discovery, and I found it because the numbers just jumped out. The 130 difference in runs saved on defense is exactly half of the 260 difference in runs scored. That's exactly half. The implication is that defense is worth about half as much as offense.

That's a lot higher than I would have guessed, and a lot higher than I think most people would guess. But the numbers are remarkably consistent from one year to the next:

Year Best to Worst Offensive Difference Best to Worst Defensive Difference Defensive Spread as Percentage of Offensive Spread
2008 264 126 48%
2007 295 141 48%
2006 241 114 47%


Everyone realizes that defense is important, but it's never been quantified. Now we have the first way to quantify it. It's not necessarily the best way, and there will be more to come on this issue. The 50% figure is more of an indicator than an exact number, but it just jumped out at me and I wanted to share it with you.
I'm not sure where the Rangers rank in 2008, so consider two scenarios: ranked near the Royals, ranked in the middle.

If the Rangers in 2008 were near the top rather than near the Royals in defense runs saved, the 2008 run differential would have been something like +64 (901 scored minus 837 allowed) rather than -66 (901 scored minus 967 allowed). IOW, a pythagorean record of 87 wins and 75 losses

If the Rangers were near the top rather than middle, the 2008 differential would've been +9 runs (901 scored minus 892 allowed) for a pythagorean record of 82 wins and 80 losses.

Basically, the Rangers would've had to have had the best defense in the majors in 2008 to have had a winning record.

That's not exactly how Dewan intended that discussion to be used, as he appears to be focused on the relative value of scoring versus preventing runs rather than how it is applied to individual teams. In that vein, his numbers suggest that the top scoring teams have more to lose by replacing mashers with slick fielding slappers than poor defending teams have to gain by the same approach. If a team is poor at both runs scored and runs saved (ahem - KC), it better invest in a player's offense first.

I think the moves the Rangers have made on defense will be productive, but I don't think that those moves alone make it substantially more likely the Rangers finish as a .500 club, since it is hard to believe they will rise to the best run saved team in the league. The good thing is that the Rangers haven't really replaced poor-fielding mashers with top-fielding slappers, which appears to be an approach that would overemphasize defense.

BTW, if anyone has the Fielding Bible 2007 and 2008, I would really like to see the change in runs saved by the Rays. They allowed 273 fewer runs in 2008 compared to 2007. Dewan's observation suggests that at most about 140 of the 273 could be attributed to improved defense. Their team FIP went from 4.70 in 2007 to 4.22 in 2008, or a decrease of 80-85 runs. It doesn't all quite add up when thinking about pitching and defense independently. There may be some synergistic relationship as the Ray's team ERA went from much above the FIP ERA in 2007 to much below in 2008 (5.53 versus 4.72 in 2007, 3.82 versus 4.22 in 2008).
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