Both of these Leinster counties will play in Division 2 of the National League next year but, as Mickey Harte feared, there was a chasm between them at O'Connor Park.
Louth came to Tullamore hoping to build on the momentum of two promotions in a row under Harte and his sidekick Gavin Devlin.
But Kildare had been competitive in the League's top tier this year and the difference in class was clear to see for the 5,308 attendance.
In the end, the sides were separated by 16 points in the rainy conditions.
“I just think our players did not deserve the battering they got on the scoreboard today," said Harte later.
"They didn’t deserve that. They worked harder than that, they’re better than that. And I’ll certainly be telling them that.”
The Lilywhites led by eight points at half-time after feeding hungrily off Louth's pointless long kick-out strategy. In that period the underdogs coughed up 10 restarts to their rivals.
To their credit, Harte's side reeled the deficit back in to five after holding Kildare scoreless for the opening 12 minutes of the second half.
But when Daniel Flynn was fouled in the 48th minute by a combination of Niall Sharkey and Donal McKenny as he was about to pull the trigger, Kevin Feely finished coolly to the bottom corner. Game over.
Louth's misery was compounded in the closing stages as Conor Grimes saw red for an off-the-ball incident and impressive sub Darragh Kirwan scored an injury time goal to add to his three-point haul for the Lilywhites.
The next destination for Harte's team is the qualifiers.
“I hope to get a team that we can stand toe to toe with, and make it a close contest," he said.
"I don’t know who that will be right now, but we don’t want a big, big hitter.
"We don’t want somebody who’s going to be just more of the same. We need somebody to give us a fighting chance. That’s the luck of the draw.”
Louth dangerman Sam Mulroy was largely shackled by a Kildare defence inspired by Ryan Houlihan.
But the Sarsfields player limped off before the end with a suspected hamstring injury that could see him miss the Leinster semi-final.
Glenn Ryan will have wanted to see his rearguard tighten up for that date after disappointing displays at the tail end of the League, particularly against Mayo.
There were signs here that it is still a work in progress. He will hope that veteran Eoin Doyle returns the next day against Westmeath in the provincial semi-final.
Fresh from scoring five goals against Carlow last weekend, Louth had hoped to rattle their rivals early on.
Liam Jackson did have the ball in the net for the Wee County before the half hour mark, but he was inside the square and the goal was disallowed.
A little earlier, Mark Donnellan in the Kildare goal denied Louth's full-back Bevan Duffy from close range and Ryan will be unhappy with the space afforded the Louth men in front of goal.
On the flip side the Lilywhites boss will be pleased that his midfield feasted on Louth's self-harming kick-out strategy.
By the 23rd minute all six of Ryan's forwards were on the scoreboard and Ben McCormack pulled the strings as Daniel Flynn looked close to his rampaging best.
In contrast, Louth finally got off the mark with Conor Early's point five minutes earlier.
The Division 3 champions were much improved from the start of the second half.
Mulroy nabbed the first score, a free from an acute angle, and Grimes swiftly tagged another couple for the underdogs.
Kildare suddenly looked uncertain but the crucial moment came when, with Duffy pushed into an advanced role for Louth and a gap to exploit, Flynn out-paced Sharkey onto McCormack's pass.
Feely stepped up for the game's first goal and handed Kildare breathing space again.
From there, there was only going to be one winner and, four minutes from the end of regulation time, Grimes was sent off for Louth after an incident with McCormack.
There was still time for subs Paddy Woodgate and Kirwan to combine for the latter to find the net.
"It was important that we started well," said Ryan, who pointed to his side's work-rate as the most pleasing aspect of their performance.
But he cautioned: "Unless we have that every day then it will be more difficult than it should be."
And Kildare's ambition now? "Ah, just keep improving with each game that we play," shrugged Ryan.
"If we improve we have some chance. If we don't, we've no chance, and so we have to look at getting better as we go along."
