As more players go back and forth, there is starting to be better data on this, but from what I've read and observed, the 12 teams in NPB are overall in the AAA range but the back end of the roster are usually filled out by younger Japanese players who would otherwise be lower minor league guys. Of course, most of the elite guys can play at a high level and Ichiro is certainly elite. But it feels like for every Ichiro, Nomo, or Tanaka there are significantly more Alex Ramirez, Alex Sanchez, Wladimir Balentien, Randy Bass, Greg LaRocca, Seth Greisinger type guys. Guys who profile as something like AAAA players in the US and go out and set records in NPB. I think that's why I view AAA as probably about right.

I think a big part of that is because teams are only allowed 4 foreign players on their 25 man. So you've got a country with 40% of the population of the US, filling out 84% of a roster in a league that's 40% the size of the MLB. In the MLB, foreign born players are 25-30% of the roster. So there are basically twice as many foreigners on MLB teams v. NPB teams. Capping foreign born players on US rosters would definitely water down down teams here and I believe that it has a similar effect in Japan, even though the league is roughly proportional in terms of population.