Tag Archives: wOBA

The gap: Hitters or pitchers?

There’s little doubt a gap exists between the Pacific and Central leagues in terms of quality, based on interleague results since 2005.

This is the second of three pieces I’m doing on the differences in quality between Japan’s two leagues.

Last time, I took up the issue of how the pitching in the two leagues differs now, and evaluated Alex Ramirez’s idea that the PL is a harder-throwing league and that the CL needs to do a better job of drafting and developing hard throwers.

This time I want to replicate a study I did a few years ago to evaluate how much of the PL’s advantage is on the pitching side. While I agree with Ramirez that PL hitters are better because they are used to seeing better pitching, this study suggests that the league’s competitive edge started in the batter’s box.

In the final piece, I’ll use my draft database to evaluate the quality of domestic player development by both leagues.

The study

A few years ago, when the PL’s superiority began to fill our rear-view mirrors like a tail-gating monster truck, I derived a study to figure out where the league’s advantage came from.

If we look at how well each team does against visitors from both leagues in their main stadiums, we can control for park and talent. If we limit the time frame to games prior to July — since interleague play runs from May to June — we can eliminate the noise from league games played in the year’s hottest months.

The study uses runs per nine innings and also wOBA, and takes a weighted average of performance against league and interleague opponents. If the PL pitching is superior we would expect offenses from both leagues will do more damage against visiting CL pitchers than visiting PL pitchers. If the PL hitters are superior we would expect visiting PL batters to do better than CL visitors.

The study suggests these conclusions:

  • The belief that the difference between the PL and CL is mostly related to pitching is unsupported.
  • CL pitching was probably a little better from 2005 to 2012, but is no longer as good.
  • PL pitchers used to struggle in the CL’s home-run friendly parks

The pitchers

I’m going to measure the quality of each league’s pitching by looking at the weighted league averages of: runs allowed per nine innings by visitors and home opponents’ basic wOBA.


Home parksCL visiting pitchers’ RA9PL visiting pitchers’ RA9
Home parksHome wOBA vs CLHome wOBA vs PL

These figures support Trey Hillman’s 2006 after the first round of interleague play that the CL was the better-pitching, harder-throwing league. But that was then and this is now. Here are the weighted averages since 2013.

The gap actually might not be as large as the tables above indicate, as I’ll go into below. It seems that size does matter when it comes to ballparks.


Home leagueCL visiting pitchers’ RA9PL visiting pitchers’ RA9
Home parksHome wOBA vs CLHome wOBA vs PL

Since 2013, whatever advantage CL pitchers might have had over their PL counterparts has evaporated, and as Ramirez suggested, the PL pitching (and defense) is definitely better than what passes for good enough in the CL.

The hitters

We’re going to flip this around and now look at weighted league averages against CL and PL visitors in home pitchers’ RA9 and visitors basic wOBA.


Home leagueHome RA9 vs CLHome RA9 vs PL
Home parksCL visitors’ wOBAPL visitors’ wOBA


Home leagueHome RA9 vs CLHome RA9 vs PL
Home parksCL visitors’ wOBAPL visitors’ wOBA

So if the PL advantage in interleague play has been primarily on the pitching side, then somebody better tell their hitters that. I did a parallel wOBA study that removed pitchers and designated hitters from the equation, but it made little difference.

The big and small of it

The one area in the study where PL pitching was inferior when measured by both visitors’ runs allowed per nine innings and opposing home teams’ wOBA was in the CL home parks from 2005 to 2012.

Former Swallows pitcher Shohei Tateyama thought that the PL was better at developing pitchers because their big parks were more forgiving. Before Fukuoka’s Home run terrace and the new shorter dimensions in Sendai and Chiba’s Home run lagoon, all six PL parks were tougher home run parks than Tokyo Dome, Jingu and Yokohama — and Hiroshima Shimin until 2008.

I broke them down into these four small parks, and three large parks, Koshien Stadium, Nagoya Dome and Mazda Stadium — more neutral than large, really. Here are the weighted averages of RA9 by visitors from each league since 2005 in the months prior to July.

2005-2008 CL visitors’ RA9PL visitors’ RA9
4 smaller CL parks4.444.94
2 larger CL parks4.244.26
2009-2012 CL visitors’ RA9PL visitors’ RA9
3 smaller CL parks3.433.80
3 larger CL parks3.613.42
2013-2019 CL visitors’ RA9PL visitors’ RA9
3 smaller CL parks4.484.57
3 larger CL parks4.193.51

That’s not a lot of information but it’s about what I expected. The steady proliferation of with three downsized PL parks would make a further breakdown since 2013 difficult and there are times when I’m adverse to work.


So that’s the footprint of the PL’s current advantage. No matter which league you play in, both leagues’ batters and pitchers playing in their home park put up better numbers when the visitors are from the CL than when they are PL teams in interleague.

When I ask people why the PL is better, the standard answer is pitching, perhaps because it’s easier to see how it could be better. But from here it simply looks like the PL pitching and hitting developed in tandem — starting with the hitting.

Next time, I’ll get into the makeup of the talent in the two leagues, and how talent has flowed into them and between them.

End of the season stuff

As mentioned in the previous post, I’ve hit a snag in my post-season work. To fill in a little bit of that gap before the playoffs start on Saturday, I was curious about which players had the best offensive seasons in NPB this year.

To measure that in a fairly simple manner, I’m borrowing standard wOBA (weighted on-base average) from Tom Tango using the stolen base version.

Here are the leaders in the CL and PL. I’ve included how many road plate appearances each batter had and their road wOBA because some might think their numbers are the product of their home parks. I’ve limited it to players with a minimum of 450 plate appearances.

CL wOBA leaders

LeagueTeamNamePA2019 wOBARoad PARoad wOBA
CLCarpSeiya Suzuki612.423312.414
CLSwallowsTetsuto Yamada641.410325.390
CLGiantsHayato Sakamoto639.410320.373
CLSwallowsWladimir Balentien468.386223.425
CLBayStarsYoshitomo Tsutsugo557.384273.352
CLGiantsYoshihiro Maru631.380320.354
CLBayStarsNeftali Soto584.374293.338
CLDragonsDayan Viciedo594.356297.325
CLGiantsKazuma Okamoto628.351325.350
CLSwallowsNorichika Aoki565.350283.351
CLGiantsYoshiyuki Kamei503.345263.334
CLSwallowsMunetaka Murakami593.341306.308
Players with 350-plus PA and .340 wOBA or higher
LeagueTeamNamePA2019 wOBARoad PARoad wOBA
PLLionsTomoya Mori5730.4082770.423
PLBuffaloesMasataka Yoshida6100.4023100.419
PLEaglesJabari Blash5270.3762780.356
PLLionsTakeya Nakamura5570.3722800.413
PLLionsHotaka Yamakawa6260.3723150.367
PLLionsShogo Akiyama6780.3683400.358
PLEaglesHideto Asamura6350.3683360.365
PLHawksAlfredo Despaigne5190.3672520.349
PLFightersKensuke Kondo6000.3663130.368
PLLionsShuta Tonosaki6210.3633120.359
PLMarinesTakashi Ogino5690.3602920.363
PLFightersHaruki Nishikawa6510.3543330.346
PLMarinesSeiya Inoue5090.3472500.347
PLMarinesDaichi Suzuki6140.3453160.330
PLMarinesBrandon Laird5530.3402890.328
PLEaglesEigoro Mogi6480.3403390.372