This should be a great World Series in large part because it’s so hard to separate the two pennant winners. The Dodgers won 104 games, but the Astros won 101. The Astros outscored their opponents by 196 runs, but the Dodgers outscored theirs by 190. The Dodgers have the possible advantage of rest, but the Astros have the possible advantage of momentum. The Astros got a midseason bump from adding Justin Verlander, but the Dodgers got a midseason bump from adding Yu Darvish. Say, the Astros might have found something by using Lance McCullers out of the bullpen. But the Dodgers have also found something by doing the same with Kenta Maeda.

When I rated all the playoff teams three weeks ago, I found the Dodgers looked the best, but the Astros were right on their heels. There’s just not much of a gap, no matter where you look. As such, I don’t think one could pick a clear favorite. Maybe you give the edge to the Dodgers, just because they could play one extra game at home. Or maybe you give the edge to the Dodgers, just because they could get the better strike zone. That’s one of the only real differences here. Technically, such a difference shouldn’t even exist, but we know that zones aren’t perfectly called or consistent, and the Dodgers have a history.

A couple weeks back, I showed that the strike zone in the playoffs is bigger than the strike zone during the summer. Within the post, I embedded an image from Baseball Savant. This shows the so-called detailed zones.

Zones 1 through 9 are pretty obvious strikes. Zones 21 through 29 are pretty obvious balls. Not every pitch taken over the plate is a strike, and not every pitch taken elsewhere is a ball, but exceptions are rare. Umpires tend to nail the easy stuff. Where there can be advantages and disadvantages is within the gray area. The border, marked by zones 11 through 19. Those are the 50/50 pitches, where umpires might be won over by good location or a quality frame.

Because I don’t want to bore you with details, I’m going to go through this fast. For every team, I found the called strike rate within the borderline zones, out of all pitches taken. I found the rate for every team’s pitchers, and I found the rate for every team’s hitters, and then I subtracted the latter from the former to find a differential. A positive differential means a team had a somewhat favorable zone. A negative differential means the opposite. Here is everything I got from the regular season, with the Dodgers and Astros both highlighted in yellow.

The Dodgers finished the year with baseball’s third-best differential. The Astros finished fifth-worst. And although the playoff samples are, of course, much smaller, I ran those numbers, too, for all 10 participants.

Dodgers second, Astros seventh. In the first plot, the two teams are separated by 5.6 percentage points. In the second plot, the two teams are separated by…5.6 percentage points. That’s a coincidence, but the pattern isn’t. Dodgers pitchers ranked third in called strike rate during the season, while the Astros pitchers ranked 17th. Dodgers hitters, meanwhile, wound up with an average called strike rate, while the Astros hitters finished fifth-highest. Put it all together and you get the idea. The Dodgers have worked with a more favorable strike zone, and it stands to reason one should expect that to remain true over the final week and a half. Weird things can happen in a best-of-seven series, but this is one of those things that’s more or less sticky.

Less is generally known about hitters taking called strikes. Much more is known about pitchers throwing them, and the story comes down to pitcher command and catcher framing. While Dallas Keuchel might have better command than almost any other pitcher in either league, one wouldn’t say he’s better than Clayton Kershaw. And the public framing metrics love both Yasmani Grandal and Austin Barnes. They’re less big on Brian McCann these days, and although I remain unconvinced the metrics do a great job of isolating the influence of specific pitchers, that doesn’t really matter, here. This isn’t a post about catchers. This is a post about the zone, and about how pitchers and catchers work together. During the season, and in the playoffs, Dodgers pitchers have worked with Dodgers catchers to expand, just an inch or an inch and a half. Though they don’t get every single call, because that would be insane, one or two calls can change an inning, which can change a game, which can change a series. You don’t need to be reminded of the difference between, say, 1-and-1 and 2-and-0. This is all baseball fundamentals.

While we’re focused on the borderline zones, I’d like to take a minute to talk about something related. When pitches were obvious strikes during the season, hitters posted a .371 wOBA, with an average exit velocity of 89.9 miles per hour. When pitches were in the borderline areas during the season, hitters posted a .275 wOBA, with an average exit velocity of 84.3 miles per hour. That’s very intuitive — it’s easier to hit pitches over the middle than pitches only kind of over the middle. Anyway, now for another league plot. I calculated, for every team’s pitchers, swing rate at borderline pitches, and then I subtracted the rates for every team’s hitters. Once again, the Dodgers and Astros are in yellow.

And now, the same data, for the playoffs.

During the season, the Dodgers were separated from the Astros by 5.9 percentage points. During the playoffs, the gap has widened, to 7.5 percentage points. This has nothing to do with called strikes. This is about pitchers inducing borderline swings, and about hitters refusing to take them. The Dodgers, as a team, have had discipline on their side. The Astros have taken a different approach, finding success through contact, or through contact suppression.

If you want to tie it all together, you could say that, when it comes to the borderline pitches, fortune favors LA. They’re likely to get the Astros to swing at some difficult pitches, and they’re likely to receive a few advantageous calls. In theory, teams should have no strike zone advantage at all, but this is how the game has been, and this is how the game remains. We’ve had that conversation before, and we’ll have it another several dozen times. Let’s just be matter-of-fact about things today. The Dodgers will probably play the World Series with a friendlier strike zone than the Astros will. It could all come down to those borderline pitches. Or it could all come down to one grooved, hanging curveball. You can never tell which it’ll be in advance.