Rugby's new Nations Championship has "logistical challenges" that can only be solved by having some teams play home games at neutral venues, a top official said on Friday.
The inaugural edition of the biennial 12-team competition is currently underway, with teams from the northern hemisphere taking on their southern counterparts.
The games are split into two blocks, with matches in the southern hemisphere being played in July before the action switches to the north in November.
There have been exceptions to the hosting schedule, with Japan hosting Ireland in Newcastle, Australia, and Fiji playing all their "home" games in England, Wales and Scotland.
Brendan Morris, CEO of southern hemisphere rugby body SANZAAR, said the competition had a "complex structure".
"There are some logistical challenges that are very real," he told reporters in Tokyo, where Japan play France on Saturday.
"With tight three-week windows, we needed to design a competition that both met high-performance and commercial needs.
"To do that, a number of matches had to be located in neutral venues."
Fiji opened their Nations Championship campaign against Wales in Cardiff before playing England at the Liverpool home of Premier League football club Everton.
They play Scotland at Murrayfield on Saturday.
Morris said there were "obvious advantages and disadvantages of that, which we're very mindful of and have worked closely with the unions in mitigating those challenges."
He also said that player welfare was "paramount in a lot of the decision-making that we have".
"There's no doubt there's some unique challenges in this tournament," he said.
"But with good planning and plenty of consultation, we're looking to get the best outcomes that we can to protect player welfare."