There is a fair degree of disappointment that Ian Madigan has not been given the number ten jersey at a time in the season when Jimmy Gopperth is not firing on all cylinders.
Maybe, coach Matt O'Connor has balanced out the fact Madigan has played hardly any rugby in the pivotal role with the proximity of those make-or-break Champions Cup tussles with Harlequins.
Maybe not: "No, not at all. The thinking was that it was probably a little bit easier to integrate him into our system there," said O'Connor.
"He's been out of it for a little bit. We wanted to take the pressure off in relation to getting his head around our detail."
This is a window in which to use Madigan given how both specialist centres Noel Reid and Gordon D'Arcy have been placed on the bench for what is an important fixture.
"With a B&I Cup game, a league game and with Europe around the corner, we haven't got the luxury of many spare bodies. It was about getting the best guys we've got available into the 23."
Thus, Reid and D'Arcy man the cold seats with returning centre Fergus McFadden and Madigan capable of moving into the back-three should injury force the issue.
The Ospreys will travel without seven Welsh internationals and a whopping 12 men ruled out through injury, including centre Ashley Beck, prop Duncan Jones, wing Eli Walker and lock De Kock Steenkamp. This is a list to rival that of Leinster's.
"Yeah but it doesn't really change our thinking. They showed last week at Ulster and all year that they're very, very tenacious," said O'Connor.
"They've been very hard to beat this year and I wouldn't expect them to be any different even though they're down on a few bodies.
"It's a pretty pivotal game in relation to the league and the standings. There are less and less opportunities to play teams above you and take points off them so that's a huge focus for us."
The 2013 U20 World Player of the Year Sam Davies is beginning to flower as a gifted left-footed playmaker with a wide variety of skills to test the best defences. The naivety, or is that fearlessness, of youth allows no room for doubt.
"If we can strengthen up our lineout and scrum to give us a better set-piece against Leinster, we can have a good crack at them," he said.
"It is just a case of sticking to our game-plan, fronting up to them physically and playing the game we want to play."
Leinster: Z Kirchner; D Fanning, F McFadden, I Madigan, D Kearney; J Gopperth, E Reddan (capt); M Bent, B Byrne, T Furlong, M McCarthy, K Douglas, D Ryan, J Murphy, J Conan.
The Ospreys: D Evans; A Natoga, A Bishop, H Dirksen, T Grabham; S Davies, M Roberts; M Thomas, S Parry, D Arhip, L Peters (capt), T Ardon, J Bearman, S Lewis, D Baker.