Leinster can help Ireland
Kearney knows Sarries are all out for revenge
What is good for Leinster can be even better for Ireland.
The winning mentality to grasp trophies that has served Leinster so well can feed into Ireland's post-season recuperation from a mediocre Six Nations.
The World Cup bid can be driven on by the Leinster contingent in the Champions Cup final, turning an ordinary season for Ireland into an extraordinary one for the Blue Brigade.
Rob Kearney believes Leinster's fifth European crown "would be a help" in Ireland rediscovering their best form in Japan.
"You want your provincial teams being as successful as possible," he said.
"The more trophies for provincial teams, the better off it is for the national team.
"It would certainly help rather than hinder."
The consistency of Leinster to challenge for honours is keeping Kearney interested in playing through the season after the World Cup.
Those negotiations are progressing at a snail's place, primarily because the 33-year-old has been concentrating on one big game after another.
Primarily, Leinster going back-to-back in Europe would contribute to restoring the Irish confidence cracked by England in Game One of the Six Nations.
Eddie Jones' England is backboned by all of Saracens best men in Mako Vunipola, Jamie George, Maro Itoje, Billy Vunipola and Owen Farrell.
The English club, unbeaten in Europe this season, will have a revenge mission in mind for that quarter-final defeat to Leinster at the Aviva last season.
The consensus opinion is that Saracens feel they owe Leinster one because they believe they are better than the Irish province.
"It's a while since they've lost in Europe, isn't it?" said Kearney.
"We are always reluctant to use the word revenge as players. But you think they will have a little bit going for them."
Saracens coach Mark McCall will point to the absence of Billy Vunipola as the main difference from last season to this.
He will also know that Isa Nacewa and Dan Leavy and Josh van der Flier were important pieces for Leo Cullen.
However, the irrepressible Jack Conan is a serious weapon Leinster were not able to summon for that quarter-final.
Certainly, Leinster are trending upwards on the evidence of their improvement from Ulster in the quarter-final to Toulouse in the semi-final.
There is a world of difference between coming back into Europe off the back of a Grand Slam in 2018 against returning from a soul-destroying experience against Wales.
When Ireland's confidence is in question, it is more difficult to gauge Leinster's performance levels.
This didn't receive a boost when Ulster came within a whisker of dethroning the champions.
Coaches Cullen and Stuart Lancaster talked up the advantage of holding players back for training rather than releasing them for PRO14 League duty.
"It makes more sense to me today than it did last week," said the veteran full-back.
"Certainly, there was a little element of uncertainty last week.
"The European build-ups, the semi-finals, they do get the best out of people.
"It is a great characteristic to have as a squad and to have players where that does happen."
The trend in improvement will have to keep rising if Leinster are to put Saracens in their place again.