HONG KONG — When casual sports fans think of rugby, they often think of it as a big man’s game.

And sure enough, if they tune in to the upcoming Rugby World Cup in Japan, they will see many large players on the field.

There are the wide bodies, the 275-pound-or-so prop forwards like Sekope Kepu of Australia, Charlie Faumuina of New Zealand or Steven Kitshoff of South Africa.

Then there are the tall timber guys — most often in the lock position — like the 6-foot-10 Rory Arnold of Australia, his 6-foot-8 teammate Adam Coleman, or Brodie Retallick of New Zealand and Eben Etzebeth of South Africa, also both 6-foot-8, and quite a few others who look like they would be comfortable in the N.B.A.

But all of those big players lean heavily on a rather large cadre of key players who are 5-foot-9 and under.