This deep into the tournament, they are mostly only flashing stats that have been accrued in the tournament, which may or may not mean much. I mean, Japan has looked really good against teams that really didn't.
That said, most people in the know consider the NPB "Triple-A-Plus." Their hitters by and large wouldn't be anything too special in the bigs - Aoki is a more-than-decent for-average hitter in the league, but doesn't have any power - and he's the only non-pitcher on an MLB roster at the moment iirc. NPB produces some impressive pitching though, that easily competes in the MLB.
Will be an interesting matchup.