The AL Is Stomping the NL Again

I read a FiveThirtyEight article not too long ago from Michael Salfino, and it had the following headline:

Who Needs A DH? The NL Is Outhitting The AL, Somehow

Now, I’d never actually thought before to just look at league-by-league OPS. And, since that article was published, the point around which it was built has become untrue. Nevertheless, by OPS, the leagues are close. Courtesy of Baseball Reference, here’s how the leagues have compared over more than the past century:

I know that’s a little hectic, but right now, the AL has an OPS just four points higher than the NL OPS. Since 2000, on average, the AL has had the higher OPS by 14 points. Hey, it’s something. And it’s enough to make you wonder, is the NL finally closing the gap? Has the National League basically caught up to the American League, in talent and performance? There’s really only one good way for us to easily investigate, and it’s a little early to be conclusive. We’re barely a third of the way into the season and into interleague play. But based on the evidence to this point in 2017 — well, you saw the headline. The NL has gotten stomped. Surprise!

Every year, there are 300 interleague contests. At this writing, there have been 103 this season, and the AL has won 61 of those. That’s good for a .592 winning percentage — essentially the Yankees’ winning percentage — and here’s how things have gone since the concept was put into action roughly a couple decades ago:

The same fact remains the same fact. The last time the NL won the majority of the interleague games was in 2003. This would stand as the 14th consecutive year of AL supremacy, and although that winning percentage is obviously far from locked in, it would be the second-highest winning percentage we’ve observed. Back in 2006, the AL won 61% of the time. In 2008, the AL won 59% of the time. That’s happened again, as the AL has refused to allow the gap to shrink to nothing.

There are levels to be analyzed, of course. Always the usual levels. Has the AL just outplayed its own performance, or something? Here’s a similar plot, only this time showing Pythagorean winning percentage, which is based on run differential instead of, you know, wins:

That’s a little less noisy, but then, that’s what you’d expect. This year, the AL is still up at .565. That would be the sixth-highest AL Pythagorean winning percentage. And the last time the AL was outscored was in, well, 2003. This is the evidence to point to when people suggest that the NL suffers from some systemic interleague disadvantage. There was no meaningful, observable disadvantage over the first seven years. A gap has just developed, and the NL hasn’t been able to close it.

There’s one more area to look at, and it’s actually my favorite area to examine, with just a third of the games or so in the bank. Wins and losses can be noisy, but runs scored and allowed can also be noisy. This, therefore, is a simple plot of OPS differential, or NL OPS subtracted from AL OPS. This would closely mirror BaseRuns performance, and any positive result shows an AL advantage. To the data!

Right. The last time the NL had the higher OPS in interleague play was in 2002. That particular advantage was all of two points, or, if you prefer, two-thousandths of one point. Last year, the NL closed to within 12 points, but the gap has since widened to 52. If finalized, that would stand as the AL’s fifth-largest advantage in the 21 seasons, although as recently as 2015, it was a pinch higher. The point simply being: The AL is still better. If you believe, that is, the results of the games played between teams in each league.

One note about that. By the end of the season, everything should be more or less equivalent. Now, though, not all teams have played the same number of interleague games. Here is the landscape of AL participation:

Meanwhile, here’s the NL picture:

Something probably stands out there. The Dodgers are the only team that has yet to participate in interleague play. And the Dodgers are good! Their so far being absent would stand to make the NL look worse than it is. But that’s making too much of the influence of one ballclub. After running the math, the AL teams have averaged a weighted .497 winning percentage against other AL opponents. The NL teams have averaged a weighted .501 winning percentage against other NL opponents. The scales, then, haven’t overall been tipped. Each league has faced roughly equivalent strengths, Dodgers be damned, and the NL has lost a whole bunch.

This isn’t anything shocking. This probably doesn’t even count as anything interesting, not now, not after so many years of writing the same articles. I think we all assumed the AL would remain the superior league, for many of the same reasons as always. How to explain how the NL is close to the AL in overall league OPS? That’s probably as simple as asserting that the pitching in the NL is weak. So it inflates the hitting numbers, which subsequently suffer when they face tough interleague opponents. Pitching might be the NL’s greater weakness, and it’s not a coincidence the NL is where the majority of the rebuilding ballclubs are found. Eventually, the NL will be better. They’ll have an advantage in talent, if not in resources.

They just haven’t had that advantage for a while. And it sure doesn’t seem like they have that advantage in 2017. There’s plenty of interleague baseball still to go. There are plenty of interleague baseball updates still to be written. If I had to guess, you probably won’t need to read them, because you’ll probably be able to guess what they say.

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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6 years ago

I wonder what the breakdown for home winning% is for interleague games. The explanation we usually hear is that NL teams are not built with a DH in mind, so they start a bench-caliber player when playing under AL rules. But is the AL’s advantage in interleague play solely due to a high home winning%? Or do they outperform typical road teams in NL parks as well?

Pirates Hurdles
6 years ago
Reply to  Yirmiyahu

Every year its the same article and every year the same question is raised and goes unaddressed.

Runaway Toastermember
6 years ago

From 2005-2016, the AL won 50.2% of interleague games in NL parks. So about even, but you have to consider that home teams in non-interleague games win about 53-55% of games. The NL is doing worse than expected, even in home games.

So far in 2017, the NL is 25-29 at home in Interleague play.

(interesting side note – League-wide home win% is surprisingly stable year-to-year, but has slipped slightly since around 2010)

I hate this discussion because it can be upsetting to fans of NL teams. Overall Interleague record doesn’t mean your favorite NL team is bad, or is a paper-champion, or anything like that. I like to think of it as someone saying something like “third basemen really suck this year, especially compared to left fielders” – even if my favorite player is a third baseman, that statement doesn’t mean *my* third baseman is bad or worse than all/most/some/any LF.

6 years ago

I wholeheartedly don’t understand being a “fan” of a league. Is it just so you have the laziest way possible to pick a side in the World Series if your team doesn’t make it?

6 years ago
Reply to  TKDC

It’s exactly as arbitrary as deciding to be a fan of a team.

6 years ago
Reply to  TKDC

It just makes your team seem less legitimate if it ends up being the champion of the “inferior” league.

6 years ago
Reply to  Yirmiyahu

I had looked into that several years ago. I don’t have the numbers anymore, but what I found was that the AL had winning records playing in NL parks suggesting talent gap had more to do with the AL’s dominance rather than a DH advantage.

6 years ago
Reply to  Troy

One could also suspect that AL clubs play their DH in the field in NL parks (1B/corner OF usually), dropping one of their lesser hitters.

Basically, the NL has 8 regular hitters to fill 8 or 9 spots, while AL clubs have 9 regular hitters to fill 8 or 9 spots. The NL is at a predictable disadvantage when they need 9 hitters, but also at a disadvantage because AL teams have a spare in NL parks.

The sample size is probably way too small to say anything definitive, but if this were true, you’d expect AL teams to have worse defense in NL parks.

6 years ago
Reply to  AaronC

The NL certainly isn’t at a disadvantage in NL parks: they need 8 starters and they invest handsomely in 8 starters (plus depth).

The AL’s “spare” is a DH which takes away resources from every other part of the roster.

The AL’s advantage, as it has always been, is that it simply has higher average payrolls (e.g. from 2006-10, it was nearly $13M higher, on average)

6 years ago
Reply to  jianadaren

The AL has the Red Sox and Yankees. The NL doesn’t. That explains most of it.

6 years ago
Reply to  Yirmiyahu

There’s a missing element in this discussion and that is that in a given year, each division only plays one other division. This year’s matchups are:

NL East vs AL West
NL Central vs AL East
NL West vs AL Central

Not only have the Dodgers played no interleague games, few NL west teams have played their divisional matchups, as opposed to their regional rival matchup.

The AL West vs NL East matchup has been most played thusfar. This matchup favors the AL, as there is a good team (hou) and two decent teams opposed by 1 good team and 3 of the 4 worst teams in the NL plus the Mets.

AL East vs NL Central should favor the AL. The ALE is the strongest division in baseball and the NLC is mediocre.

The NLW has 3 strong teams and the ALC has probably one. I’d expect the NLW to win more than 50% of its games vs the White Sox, Tigers, Royals, Twins and Indians. Even the giants should do well vs the bottom of that barrel as CHW, Detroit and KC are poor teams.

I suspect it will end a lot closer than it is now, even if it doesn’t end even. The games most favorable to the NL haven’t been played at all yet.

It’s not just that the Dodgers are a team that we think should win 60% of their games and they haven’t played and by. Their opponents quality will be so low they should probably win 2/3 or more of their interleague slate of 4 LAA sans Trout, 3 Cle next week, 3 KCR before the all star break, 3 Det post-trade deadline, 4 cws and 3 min.

And this is also true if less dramatically for Col and Ari.

6 years ago
Reply to  mikejunt

The Marlins are better than the Padres and Reds, at least.