Defense Is At Its Best In October, Too

Hello! Do you like baseball posts about how the playoffs are different? You have come to one of the right places.

Let’s go over some easy stuff. The playoffs, just by being what they are, select for the best baseball teams. Playoff rosters are selective for the best hitters, and they’re also selective for the best pitchers. Because of the nature of the series, and with all the off days, you see bullpens used more aggressively. We wrote about that yesterday, and everyone has written about that on every day, for the past few weeks. The Indians are in the World Series, and they mostly have their bullpen to thank, and, yeah, that’s the big story in the AL as we wait to identify the other half.

I want to talk briefly about how defense factors into this. Maybe it’ll surprise you, or maybe it won’t, but come playoff time, even batted balls themselves more often meet a negative fate. Strikeouts tend to go up, and homers tend to go down, but even when you concentrate on plays where hitters knock the ball fair, you still see things favoring run suppression.

I linked once before to this recent Ben Lindbergh article about the Blue Jays. I’m sorry about that timing, Blue Jays fans, but something in there jumped out to me, something that was almost a throwaway point. Quote:

Defenses are stronger in October, too?—?this year’s Cubs, for instance, have held opponents to a historically low batting average on balls in play. From 1995–2015, the league-wide batting average on balls in play was .298 during the regular season, but only .284 in the playoffs.

So let’s think about that. Or, let’s even examine that. You’re already familiar with BABIP. I’m going to use that, and I’m also going to use SLGBIP, which is the same thing, but giving some extra credit to doubles and triples. The stats pretty much tend to mirror one another but there’s nothing wrong with being more thorough. Here’s a plot comparing the playoffs to the regular season over the wild-card era:


What you see is essentially what was quoted. In the playoffs, BABIP is lower, and SLGBIP is lower. Only once in this window has there been a higher playoff BABIP than regular-season BABIP. Only twice has there been a higher playoff SLGBIP. Clearly, batted balls just kind of do worse when October rolls around. I’ll note that, so far this year, playoff BABIP is down by 35 points, which is the biggest gap observed. Playoff SLGBIP is down by 47 points, which is almost the biggest gap observed. So, it’s not just that the pitching this October has been tough.

You might now pick up on the fact that this analysis is leaving something out! This is comparing performance among playoff teams to regular-season performance among all teams. Let’s fix that. Here is how the playoff teams have done during the regular season, compared to the league-average teams.


Sure, over the whole wild-card era, the average regular-season BABIP is .298. However, the average regular-season BABIP just for playoff teams — weighted by number of playoff games played — is .293. For SLGBIP, the difference is .379 and .370. What this is showing is that the playoffs have been slightly selective for better team defenses, which isn’t a total surprise. And, yeah, pitchers might be a small part of this. Can’t really separate the two. Anyway, glance over at 2016 — this year’s playoff teams were 15 BABIP points better than average during the year. That’s the biggest gap in the era! Thanks, Cubs! Particularly good defenses also showed up in 2002. That’s the last time there was such a big difference in playoff-team SLGBIP.

Now we can close this out. This time, let’s compare playoff statistics to the regular-season statistics of just the playoff teams. It’s like an adjusted version of the first plot. I didn’t make any adjustments for roster construction so this isn’t perfect, but it should be most of the way there.


Remember how 2002 was arguably the last time such good defensive teams made the playoffs? Funny enough, that October, defenses underachieved. Even in the playoffs, on average, teams do better than their regular-season BABIPs by 10 points. They do better than their regular-season SLGBIPs by 16 points. Above-average defenses have become even more above-average, and just so far this month, the BABIP gap is 20 points. The SLGBIP gap is 27 points. Those are bigger than usual, following a decade or so of the playoffs more closely mirroring the regular season.

The playoffs select in part for better-than-average defensive units. For what I imagine is a variety of reasons, in the playoffs, those defensive units get even better. Balls in play are turned into more outs. Defensive liabilities probably get less time. The weather is colder. Hittable pitchers pitch less, and relievers pitch more. It’s not like everything should favor the run-suppression side — remember, the playoffs also select for above-average hitters. But their ability doesn’t counteract everything working against them. Hitters look mostly like themselves, but everything is made just a little bit worse. It’s harder for them to hit the ball, it’s harder for them to hit the ball out, and it’s harder for them to find a part of the field where there isn’t a defender stationed nearby.

You could try to look in here for developing trends. Is October defense getting even better? Are teams, say, able to better prepare, and/or exploit things they notice as series progress? There’s more to explore, I’m certain. For now, the important thing to understand: Hitting in the playoffs is incredibly hard. Everybody already knew the pitchers are almost exclusively terrific. There are also fewer holes available around and behind them. Put it together and there are hitters who might argue the playoffs are a little bit rigged.

We hoped you liked reading Defense Is At Its Best In October, Too by Jeff Sullivan!

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Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.

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I feel defense has been pretty shoddy for the most part in the post season, based on the eye test anyways. Balls do not look like its jumping off bats, I suspect the exit velocity (better pitching, balls, etc) might be lower in the post season and accounting for the lower numbers