Ireland's hard-fought 22-13 win over Scotland in the Six Nations on Saturday lent weight to the suggestion that Japan should target the Scots when the three sides battle to progress from Pool A at the Rugby World Cup later this year.
Hosts Japan know they will almost certainly have to beat one of the European heavyweights to reach the quarterfinals by finishing in the top two of a group that also includes Russia and Samoa.
Bruised by a chastening defeat at home by England last week, defending Six Nations champions Ireland - the 2018 World Rugby team of the year - needed a reaction at Murrayfield.
But Scotland, who have been revitalized almost beyond recognition in recent years, had the world No. 2 side on the back foot for much of the first half, especially when their exciting backs got on the ball and unleashed their renowned passing game.
Ireland, however, showed grit and superb game management to just about keep themselves ahead on the scoreboard and then edged out of touch as Scotland's performance disintegrated in the second half.
Scotland captain Greig Laidlaw admitted their second-half errors cost them the game, saying, "We released the pressure valve."
His coach Gregor Townsend took responsibility, saying Scotland had to improve their set-pieces.
"Both teams' energy levels dropped in the second half, but they were more accurate than us and that was the difference," he said.
Swashbuckling and incisive in the first half -- especially when star fly-half Finn Russell intercepted, burst clear and superbly set up Sam Johnson for a galvanizing try -- Scotland lost composure after the break, and a series of unforced errors and penalties gave Ireland the initiative.
It will have been infuriating for Townsend -- and of great interest to onlooking Japan coach Jamie Joseph.
Townsend took over from Vern Cotter in 2017 after the New Zealander had restored hope and pride to a Scottish side that had been in the doldrums for 15 years. Cotter made Scotland tougher and took them from 10th in the world to fifth, while Townsend has developed a more adventurous, high-tempo passing style of play.
They have beaten England, Australia, Ireland, France, Wales and Argentina in the past two years, while Edinburgh and Glasgow -- who contribute about three quarters of the national team's players -- have both reached the last eight of the European Champions Cup, the first time two Scottish clubs have done so.
But old failings still surface. Scotland, now ranked seventh, may have cruised to a 33-20 win over Italy last week, but they lost concentration and conceded three late tries that took the shine off the performance.
Ireland would always punish such sloppiness more ruthlessly and Japan's coaching team will have noticed how decisively they capitalized on Scotland's lack of discipline and accuracy in the second half.
Ireland coach Joe Schmidt praised his team's set-pieces and ferocious defense, but said the key difference from the week before was their attitude.
"There was a definite rise in temperature and increase in energy," he said.
Scotland had shown so many positive attributes in the first half, despite a terrible mix-up between their wings Tommy Seymour and Sean Maitland that gifted the first try to Conor Murray.
They also lost key man Stuart Hogg to injury and fell further behind to a wonderful try by Ireland's star wing Jacob Stockdale, the result of a stunning strike move no doubt meticulously planned by Schmidt.
Ireland fly-half Johnny Sexton was forced off after being struck by a series of big hits, the heaviest in the build-up to their second try. "Because he is who he is that's going to happen and Johnny probably knew he was only going to play 20 minutes so he jammed it all into that time," Schmidt said.
Everyone waited to see if the theory that Ireland are overly reliant on the 2018 world player of the year would be proved correct. However, replacement Joey Carbery was excellent, not least when lofting a superb long pass to Keith Earls for the try that seemed to kill off Scotland.
Ireland had lost the physical battle against Eddies Jones' England team, prompting a week of soul-searching, but Scotland were never going to beat the Irish in a similar way. Like Japan will need to be at the World Cup, Scotland had to be smarter, more creative and faster -- and in the first half it looked like they were well on their way.
But a key period just before half-time saw Ireland heroically and desperately hold off a Scottish attack that lasted 25 phases. Scottish hooker Stuart McInally denied his team was demoralized to still go in behind, but admitted they were "knackered" in the second half.
"Why did we have such a good first half and not play the same in the second half?" Russell asked. "What changed? It's frustrating as you love going up against the best teams in the world, and we get close, but come up just short. If we're going to progress we need to start winning these games."