Scramble back 12 months and the province was pitching up in Coventry for a game that meant nothing to them and everything to their hosts.
And it showed.
Wasps hit them for 51 points that day, securing their own place at the top of the pool and condemning the three-time champions to a fifth loss in six games.
Turn back towards this evening at Stade Pierre Antoine and the situation is almost a mirror image with Castres devoid of interest in Europe beyond this schedule filler and Leinster already qualified for the quarter-finals but with the carrot of a home berth still to drive them on.
The benefits to them of securing a date at the Aviva Stadium come the start of April, both financial and on the field of play, can hardly be overstated and it would stand as a major blow were they to lose this evening and face the prospect of another road trip post-Six Nations.
“It’s about doing ourselves justice here,” said head coach Leo Cullen. “We’ve done well and we’ve played quite well, bar a couple of games that didn’t go to plan, but to be able to come out of this section of games pretty happy with what we’ve done…
“We’d take a win in this game and having a good defensive effort and putting together some of our plays pretty well. So not to just scrape a win, (but) to win the way we want to, to win playing the rugby we want to and put together that sort of game.”
Win and that Dublin date is theirs but they will have to secure it without Sean O’Brien who is again absent as a result of what Cullen labelled as either a minor calf strain or tear that has sidelined him since Zebre at the start of the month but which, he believes, won’t cause him to miss the start of the Six Nations.
Jack Conan showed last week when claiming three tries in the rout of Montpellier that Leinster are well equipped to cope with the absence of even the most important of squad members at this stage of the season, even if it is a big day for Ross Molony who replaces the suspended Hayden Triggs at lock.
More than anything, it is that depth that signifies their strength.
Cullen has five Ireland internationals poised in reserve tonight, another two for whom senior Irish honours are a matter of when rather than if and an accomplished scrum-half in Jamison Gibson-Park who lined out eight times for the Maori All Blacks before moving to Dublin.
The Kiwi has had to bide his time on the pine and watch Luke McGrath grow into the starting role to such an extent he is now a good shout to cover for Conor Murray during the Six Nations and another man for whom patience has been a difficult virtue is Cian Healy.
Only injury prevented the loosehead from starting for the British and Irish Lions against Australia four years ago but more injuries have stunted his career trajectory since and to such an extent that he is now eager to avail of a rare starting berth in place of Jack McGrath.
Still only 29, Healy has plenty of time to reclaim the heights his career hit in his early 20s but his frustrations and eagerness hurt him on another start back on St Stephen’s Day when he worked himself into a tizzy beforehand and gave away a pair of penalties in the 12-point defeat.
“I’m just trying to take every opportunity that’s been given,” he said. “The Munster game a while back, I performed poorly on the discipline front, and that was itching away at me a bit. You can’t afford to do that when you’re given the opportunities. Apart from that, it’s been edging away in the right direction.”
You could say the same for Leinster as a unit. Pool 4 has been a far smoother ride than it appeared at the start of October but, though stiffer tests remain, the manner in which the province has moved on from last year’s European debacle by injecting youth into the team and the experience of Stuart Lancaster into the brains trust has been seamless.
Gone now are the questions over Cullen’s suitability for the post.
“Decisions are still very, very tough and a lot of thought goes into everything that we do here,” the head coach said. “As a coaching group you are always learning. When we started off with John Fogarty, Girvan Dempsey and myself the three of us were all new to it.
“But when Kurt (McQuilkin) moved back to New Zealand, having Stuart involved, the fresh eyes have definitely been a real benefit to the group in terms of what he has added. All the while players are looking to self-improve and us at coaches are very similar.”
Tonight should provide further proof of that.