Tonga could be backed for a maiden World Cup title, with a former tournament star endorsing the side's chances.
Australia's halfback selection is also in focus after Mitchell Moses was ruled out of the competition, leaving coach Kevin Walters to consider his options.
Sam Walker was not certain to be first choice after his premiership-winning campaign with the Roosters.
However, Moses' long-range kicking had made him a strong candidate to partner Cameron Munster, whose style is more instinctive.
New Zealand is still hoping Kalyn Ponga might return during the tournament, while Australia has already lost Moses.
Jack Bostock's market value has also become a talking point after his impressive international debut for Australia.
These were among the main issues to emerge in the World Cup's opening week.