Leo Cullen will put Leinster's perfect PRO14 record to a true test in Glasgow this evening.
No matter the outcome, the coach will learn far more from what happens than in the routine RDS demolitions of Ospreys (53-5), Edinburgh (40-14) and Dragons (50-15) and even the crushing of Connacht (42-11) in Galway.
Cullen has taken the view to completely change Leinster's team, Ross Molony taking over the captaincy beside Devin Toner in the second-row.
This is a luxury allowed by the Blues' fast start which has them nine points in front of Ulster in Conference A with Glasgow a whopping 14 points behind.
Half-backs Jamison Gibson-Park and Ross Byrne, Toner, flanker Josh Murphy and hooker James Tracy complete the quintet of replacements moving from the Champions Cup reserve bench to first-team action.
Of course, this is a renewal of the PRO14 final at Celtic Park when Leinster spoiled the party.
That was a bitter pill to swallow for Glasgow and the last memory from a failed season.
Backs Tommy Seymour, Sam Johnson, Ali Price and forwards Jonny Gray and Rob Harley started in the final. They will be out for some small measure of redemption.
Leinster coach Stuart Lancaster said: "The PRO14 will be a huge motivation for Glasgow. They'll need the points for sure.
"That, plus the final from the end of last season, the quality of players they've got, the quality of coaching staff they've got, we know it's a full-on game."
It will serve as a teaching tool for Lancaster as Leinster are almost guaranteed to be on the back foot for the majority of the 80 minutes with No.8 Caelan Doris, back from injury, scrum-half Gibson-Park and Toner the stand-out candidates to make a case for Europe.
The unrelated O'Briens, Jimmy and Conor, will man the midfield berths supported by a capable back-three in Adam Byrne, Hugo Keenan and Cian Kelleher.
Glasgow coach Dave Rennie will leave his post at the end of the season to take over Australia.
"Leinster have great depth and have been the form team," he said. "They are very well-coached, are playing with great confidence and have threats across the park. We'll need to be at our best to get a result."