Well, that has just blown the World Cup right open for Japan, for Scotland and for Ireland.
Joe Schmidt's men have lost control of Pool A and must look to a favour from Scotland to get it back.
Essentially, the destiny of the quarter-finalists will all be decided in the final game of the group when Japan will look to do to the Scots what they did to the Irish in Yokohama on Sunday, October 13.
The danger of making any presumptions in Pool A has been exploded by what the hosts did to Ireland's high expectations.
Where Scotland would have been depressingly down after the first weekend, they now have a chance to rebuild their confidence against Samoa in Kobe City on Monday (KO 11.15am Irish time).
Ireland should be able to take 10 points away from Russia next Thursday and Samoa on Saturday, October 12, to leave them on 16. Should.
Even if Scotland can reel off three bonus-point victories, it would still limit them to 15 points, one behind Ireland.
Japan will win the Pool with two more wins against Samoa and Scotland
Even if Japan take five points away from Samoa, it will put them on 14.
This would make them vulnerable to defeat to Scotland, who should be on ten points from Samoa and Russia on Wednesday, October 9.
Gregor Townsend would overtake The Cherry Blossoms with a bonus-point or even four points because they would be tied on 14 and Scotland would progress on the head-to-head result.
Either way, Ireland's best-case scenario is for Scotland to do them a favour to resurrect that quarter-final against South Africa.
The next best is for Joe Schmidt to have to scheme for the All Blacks as a Runner-up in Pool A.
The worst-case scenario, a loss or draw to Samoa or Russia, doesn't bear thinking about.
Even then, they could still progress as long as Japan defeat Scotland.
PREDICTION: Scotland to beat Japan in the final test of the Pool and Ireland to qualify as Pool A winners with Scotland as the runner-up.