The defeat hardly constitutes a surprise but the manner in which Leinster capitulated in beautiful Bordeaux should be a cause for considerable concern. The visitors teased their small travelling band of supporters with an excellent opening 38 minutes only to perish, largely by their own hand.
Leinster's 10-points advantage at that juncture was a merited reward. Shorn of eight first-choice players, the province could hardly have harboured great expectations, but to their credit of those who deputised, principally Hubie Kos, Shane McEntee, Pat Ward and Declan O'Brien, they grasped the opportunity with gusto.
What transpired after the interval, though, could not have been more marked in contrast. It was difficult to reconcile the two extremes. Leinster's performance, initially epitomised by character, determination and flair, degenerated, almost seamlessly, to gross incompetence.
Juvenile errors pockmarked every attacking gambit: ball was turned over in the tackle, possession carelessly kicked away, the basic skill levels were abominable and would have not been acceptable in mini-rugby. The Leinster three-quarter line could not string three passes together, that is on the occasions that out-half Alan McGowan did not aimlessly kick away possession.
The visitors' sudden malaise coincided with a more intelligent appraisal of circumstances by Begles-Bordeaux. A slavish addiction to using centre Thomas Ossard on a cut-back option was both predictable and poorly constructed, often allowing Leinster to make tackles behind the gain line.
Begles amended their gameplan, the emphasis switching to punching holes on the fringes up front and adding dynamism to the driving and mauling. The new approach coupled with intermittent tackling from their opponents, paved the way for a points fest.
On the occasions Leinster did manage to secure possession, they simply turned it over almost immediately offering no respite from a constant diet of tackling. Olivier Brouzet, providing a fine platform out of touch, became more prominent in the loose and his example was taken up by flankers Francis N'Tamack and Leon Loppy.
The shackles of frustration removed, Begles produced some irresistible rugby, albeit facilitated by a spiralling error count from their opponents. A well-worked try from prop Frederic Garcia just before the interval was quickly improved upon five minutes after the re-start with a second from Brouzet.
It was then that Leinster self-destructed on a huge scale. David O'Mahony's quick 22 led to a turnover and a penalty which Cyril Schuwer kicked, quickly followed by a try from full-back Jean Marc Souverbie.
When a mix-up between Ciaran Scally and Kevin Nowlan inside the Leinster 22 caused another spillage, Schuwer accelerated on to the ball and crossed under the posts. Pascal added the conversion and Begles led 25-10. Two further penalties from the out-half simply embellished victory.
Mike Ruddock must pick up the pieces prior to next Friday night's winner-take-all clash with Llanelli at Donnybrook, no easy task given the casualty list.
At this stage John McWeeney and David Hegarty are out, Victor Costello (ribs) and David O'Mahony (hamstring) are almost certain to be absent while Trevor Brennan, Brian Carey and Pat Holden will require physio Alan Kelly to produce minor miracles.
Kurt McQuilkin offered a physical presence defensively in the centre, but he, too, is now nursing an injury and his belief is that Saturday was his last representative game.