Tonight will certainly provide an answer to that, as the two giant southern sluggers, New Zealand and South Africa, climb into the ring in Yokohama and dispute what will be the top-billing decider in Pool B.
The World Cup cannot be won on the first weekend, but history suggests it can be lost — no winners of the Webb Ellis Cup have been defeated in a pool game.
The champions are not the only game in town, across what is the most riveting opening schedule for a World Cup. The first game, Japan against Russia at the Tokyo Stadium last night, may not have had blue-chip status on normal fixture cards, but 40 million people were set to tune in across Japan alone.
"Everyone understands how important this event is to Japan," said Michael Leitch, the Brave Blossoms captain and billboard boy from the 2015 World Cup.
Not only is this the most competitive World Cup ever, with six, perhaps seven, genuine contenders, it has also been set up to hit viewers in the eye with several fixtures that would not be out of place in the knockout stages.
Perhaps this is a sign of nervousness among organisers that a tournament held in a non-traditional territory might be perceived somehow as flaky and under-clubbed if it did not grab the attention from the first whistle. Take your pick thereafter: Australia against Fiji, a riot of movement; Argentina versus France, a nerve-shredder for the loser in the toughest of the pools alongside England, who put their bodies as well as credentials on the line in Sapporo tomorrow, a few hours before Ireland face Scotland.
Then Wales make their bow on Monday with Rob Howley's expulsion still reverberating. Warren Gatland, though, is a master when it comes to dealing with difficulty.
Much as they would not wish to be so challenged, there is a sense that Wales might dig even deeper.
England have been in the Lotus Land of Miyazaki, all lush and steamy before, suitably enough, encountering the chillier climes of Sapporo in Japan's northernmost island of Hokkaido. A World Cup is no place for self-indulgence and England are aware that even though tomorrow's opposition Tonga were beaten 92-7 by the All Blacks recently, there will be a hard-edged, muscular tone to every contact.
England ought not to be unduly troubled by either Tonga or the fast-improving United States four days later in Kobe. But Argentina and France are different propositions. Either could give England a bloody nose. Eddie Jones will be judged on how far England get. A semifinal (against the All Blacks, perhaps) is the minimum requirement. So much has been invested in this campaign, so much of Jones himself, that it would be crushing for all concerned if they were to come up short once again.
It is such a rite of passage to salute New Zealand's hegemony at the start of a World Cup that you have to remind yourself that it is Ireland who head the world rankings — 12 months ago, there would have been no such oversight. Ireland can allay any anxieties with a rousing opener against Scotland.
It is time for defining acts from the star turns, belligerent defiance from the underdogs and, yes, maybe another miracle. Some 400,000 overseas fans are expected. A treat awaits.
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