The six head-to-head battles in this weekend's inter-pros that could sway Joe Schmidt
Players get chance to stake claim for South Africa tour as provinces face off
The focus on the pitch is all about the race for Guinness Pro12 play-off spots, but in the stands Joe Schmidt and his coaching team will have his notepad out as they continue to assess options for the summer tour of South Africa.
Over the next 48 hours, the four provinces will collide in front of more than 60,000 spectators in the games which the Ireland head coach believes are the closest thing the players will come to Test rugby for the rest of the season.
The New Zealander talked about these games having "a real edge to them" in the aftermath of the Six Nations and there are a number of personal duels that will have an extra bite at Kingspan Stadium and the Aviva Stadium as the jostling for squad positions steps up a notch.
Jared Payne v Robbie Henshaw
Schmidt grew increasingly irritated by suggestions he should break up his first-choice centre partnership during the Six Nations amid calls for Payne to shift to full-back to accommodate Stuart McCloskey, so it is intriguing to see Ireland's No's 12 and 13 donning the No 15 shirt in Belfast tonight.
Connacht's decision to redeploy Henshaw to full-back is one of necessity as Tiernan O'Halloran is out injured, but Les Kiss has opted to retain McCloskey and Luke Marshall in his midfield; meaning Payne remains in the back-field.
For all of the New Zealander's resistance to the idea, there is an argument that both players are operating in their best positions tonight; albeit playing the role with very different styles.
Payne's reading of the game and ability to counter-attack make him a compelling figure at full-back, while Henshaw has the ability to choose the right moments to come into the attacking line as he did against Munster at Thomond Park earlier this season.
Both are strong under the high ball and offer threats if the kicks in their direction are not accurate. Playing at full-back for Ireland may not be on the agenda for either, but this is a chance to show Schmidt what they can do.
Rob Kearney v Simon Zebo
Sticking to the full-back theme, this is a mouthwatering head-to-head that may not yet take place as Leinster's Kearney attempts to prove his fitness, while Zebo may end up on the wing for Munster. One imagines that Kearney will be doing everything in his power to get a run at the Aviva Stadium, however, particularly in the kind of conditions where his strength under the high ball is likely to come to the fore.
Zebo finished the Six Nations in the No 15 jersey and did everything possible to take his chance when the Louth man's troublesome hamstring flared up, but Kearney has been Schmidt's go-to man throughout his time in charge and is still favourite to get the nod in South Africa if he can stay clear of injury.
The Cork native shifted to full-back for his province last weekend against Zebre and managed to break Anthony Horgan's all-time try-scoring record and could hold on to the shirt.
A collision between this pair should make for very interesting viewing for Schmidt.
Josh van der Flier v Tommy O'Donnell
These two must not know quite where they stand after a rollercoaster Six Nations, but tomorrow they get to take out any frustration in front of a big crowd at the Aviva Stadium.
It should be tasty as the opensides look to influence proceedings and catch the head coach's eye, with their own distinctive styles.
You got the impression that Van der Flier was a marked man in the Sportsground last weekend as Bundee Aki made a bee-line for him at every opportunity, but the Wicklow native continued to make his tackles and came up with a big turnover late on.
O'Donnell bounced back from losing out to the younger Leinster player by performing well against Scotland, but he'll have to match Van der Flier's discipline while making his big carries to make an impression.
With Peter O'Mahony, Iain Henderson and Sean O'Brien expected to be back for the tour, the back-row places will be squeezed, so this is a big weekend for both players.
Andrew Trimble v Matt Healy
The internet erupts weekly with calls for Healy to be capped as he continues to score try after try for Connacht and tonight he gets to come up against an experienced international who started all of Ireland's games in this year's Six Nations in Trimble.
The forecast for rain tonight would appear to favour the Ulster man who played well without breaking free during the Six Nations and will be aware of the former Lansdowne wing's impressive form after he spent time in Ireland camp at the end of the Six Nations.
It's a clash in style and should give Healy a real test of his defensive credentials.
Jamie Heaslip v CJ Stander
O'Mahony's impending return is set to make life interesting in Ireland selection meetings after CJ Stander's barnstorming contribution during his first Six Nations.
Throughout Schmidt's time in charge, the starting back-row has been O'Mahony, O'Brien, Heaslip; but the emergence of Stander has offered an alternative and he has played well at No 8 for his provincial side this year.
Heaslip grew in stature as the Six Nations progressed and will be fully aware of the first true rival to his jersey since Denis Leamy retired.
Expect some earth-shuddering collisions.
Donnacha Ryan v Devin Toner
Partners in crime at the end of the Six Nations, the return of Iain Henderson to the Ulster jersey will put pressure on both Ryan and Toner if they want to continue in the starting slots this summer.
With the conditions set to be treacherous at Lansdowne Road tomorrow, the lineout battle will be key as these Ireland colleagues look to outsmart one another after working in tandem for two months.
Ryan would appear to have the edge in open play, but Toner has been punching his weight in recent weeks. It should be tasty.