Paris last month was agonising. A four-point loss and little more than the width of Jordie Barrett’s hand between ultimate defeat and a place in the semi-final and, with Argentina next up, an almost guaranteed place in the decider itself.

A night like that is always going to hothouse regrets.

“Because it’s such a close game, you look back at every mistake you made or something you felt you could have done better and you’re like, ‘If I had just done then better, that would have the difference or if this had just gone right or if I’d ran that line...’ 

“Do you know what I mean? All those kinds of things, which does make it a bit more difficult. So, that was one of the things I found a lot tougher,” said van der Flier who is set for a return with Leinster this weekend against the Scarlets.

“You have to go back to your process and say if you’d done everything you can in the build-up, and you made every effort you could, then you are kind of happy with that, but it is hard in reality to do that.” 

Hard to believe but that was a month ago now.

Van der Flier and the rest of Andy Farrell’s squad were given time off on their return home so that they could rinse the worst of the disappointment from their hair and report back to their provinces with their minds and bodies renewed.

He found himself in a bit of “a no man’s land” at first. Gone was the daily schedule, the short-term focus and collective bonhomie. And it was too soon to just switch back into Leinster mode. It took readjustment but the break ultimately did him good.

“Once the World Cup was over then, once the final had happened, there was no feeling of ‘oh, we could be there if it had just gone our way.’ It was kind of just a line in the sand, ‘it’s over now, let’s move on’.” 

So, he’s had the rest but a change is just as good at times like this. If every new season brings with it fresh faces and new ideas then Leinster are experiencing a heightened version of that with the absences of Johnny Sexton and Stuart Lancaster and the imminent arrival next week of one Jacques Nienaber.

Van der Flier took the time to say a quick hello after the South Africa-Ireland pool game at the Stade France during the World Cup and he made a point of asking some of his Munster colleagues for a word on their new addition too. The feedback was all positive.

The departure of Lancaster to Racing 92 will mean Andrew Goodman assumes complete control of the attacking brief, but most eyes will be on the defensive side of Leinster’s operation in the months to come as Nienaber gets to work on that side of the ball.

The Boks brought a frightening linespeed to their pool opener against Scotland in Marseille and never let up in that regard throughout the tournament. Leinster’s ‘D’ has been decent so how these two stars align will be interesting.

“I don't know if he might come in and say we're defending the exact same way that South Africa do, or he might like some of the stuff we do and change it, I'm not really sure, but it's definitely exciting,” said van der Flier.

“Looking at any of the teams he's coached, the way they defend, it's a pretty exciting way to defend. It's quite aggressive and you're definitely on the edge of your seat watching that defence. It seems exciting to be a part of.”