Murphy's stout resistance helps young back-row come to the fore for Leinster
Jamie Heaslip played on for a few minutes but even the indestructible No 8, whose DNA seems to have been designed by NASA scientists, couldn't stand the pain for much longer.
A damaged AC joint may not be too serious but the sight of the captain trudging wearily from the fray, his first premature departure from any contest since December 2010, indicated that matters could become grave for his side.
After being absent for humiliation in Limerick, it was expected that his return could galvanise his shell-shocked side, particularly when veteran Shane Jennings succumbed to his worrisome hamstring even before a ball had been kicked.
Even though he only lasted 27 minutes, only Devin Toner of his forwards made more tackles (10-7) than Heaslip.
His removal meant that, in all, Leinster were now deprived of six back-row stalwarts - all of whom are Irish internationals - and an opening half of glacial ruck ball hinted at a worrying outcome.
No matter. Jordi Murphy (right) is a Six Nations champion and, still recovering from a three-month absence due to shoulder surgery, he slotted in at No 7 for Jennings before moving again to deputise for Heaslip.
Josh van der Flier, with only his debut against Zebre before Christmas as a stepping stone, demonstrated little anxiety as he became the third openside of the day, while Jack Conan strode towards a second man of the match award in recent weeks as if he were a ten-year veteran.
The back-row trio of tyros were all born in the 1990s.
"The back-row were excellent, the composure they showed in dealing with so much disruption before and during the match," enthused O'Connor.
For Murphy (left), there has been little time to contemplate how the pecking order at the province - and for Ireland - can change so suddenly.
"I don't think I've ever been out for that long before so it was a bit of a shock in the first few games," he said. "You're three months behind everyone in game-time really. It's definitely taken me a while to get up to speed. I'm not there yet but this was definitely a stepping stone.
"It's not frustrating. It's just what I have to do. I can't get left behind. I can either feel sorry for myself and fall further behind or else put my hand up and keep moving forward.
"I'm delighted that I have that game-time under my belt. But I have to keep pushing on.
"That's the relentless nature of the back-row in Leinster. Nobody gives you any breathing space.
"Jack has had some incredible performances. Dominic (Ryan)has had some great displays too and even earned a cap out of it. It's relentless."
Heaslip's shoulder damage is not believed to be significant, according to Leinster, while Tommy Bowe's withdrawal after a knock to the quad was also precautionary and there is little anxiety about his fitness.
They may be some residual anxiety within Leinster about a potential citing for Jack McGrath after a stamp on Rory Best, one which left BBC pundit Maurice Field hoping that "he gets done for a long time", though the Ireland prop had himself been stamped upon earlier by an Ulster player.