Separated by points difference in the league season after finishing level on 70 points in Conference B, the two sides know each other very well, having faced off three times already this season.
Leinster are unbeaten against Scarlets so far, winning twice at the RDS Arena, once in the Champions Cup, and coming away from Parc y Scarlets with a 10-10 draw.
But that form will count for very little on Saturday, with Scarlets heading into the game full of confidence after their 28-13 semi-final win over Glasgow Warriors.
Leinster showed great resilience to keep Munster out in their semi-final, winning 16-15 a week after beating Racing 92 to the Champions Cup in Bilbao.
There will be key battles all over the pitch, but we have picked out two head to head clashes that could prove pivotal in deciding who lifts the coveted Guinness PRO14 Trophy on Saturday.
James Ryan v Tadhg Beirne
Tadhg Beirne will be desperate to help Scarlets defend their title in the same week he was called up to the Ireland squad for the three-Test series in Australia this summer.
The Scarlets lock is moving to Munster at the end of the season and is eligible to play international rugby, richly deserved after another fine season.
Beirne ended the regular season with 37 turnovers won, 15 more than any other player in the Guinness PRO14 and is a key threat to Leinster at the breakdown, something they worked hard to stop during their Champions Cup clash.
— Scarlets Rugby (@scarlets_rugby) May 24, 2018
But at lock he goes head to head with another Irishman who has been in superb form since breaking into the Leinster side.
James Ryan is yet to taste defeat in his professional career, with the 21-year-old enjoying 22 wins from 22 games for club and country.
A defensive stalwart and hugely effective with the ball in hand, Ryan was man of the match in Leinster’s European triumph.
The two second rowers offer something different to their respective teams, but both are capable of making a match-winning difference.
Jonathan Sexton v Rhys Patchell
Scarlets fly-half Rhys Patchell will be up against it against Johnny Sexton, according to Scarlets head coach Wayne Pivac, who admitted that Patchell is still developing as a fly-half, while his opposite number is a world-class operator.
But Patchell, seven years Sexton’s junior, has been excellent for Scarlets this season and has cemented himself in the side, versatile in being confident at fly-half and full-back.
The 25-year-old enjoyed a superb Six Nations debut for Wales against Scotland earlier this season and has contributed points in tries and from the tee as Scarlets aim to defend their title.
Patchell has already proven that he can handle the big occasion, but will be keen to get the better of Sexton.
“We probably owe Scarlets one in the PRO14.”@jackmc100 looks ahead to Saturday’s #GUINNESSPRO14 Final against the reigning champions at @AVIVAStadium. 👇#OneMoreRoar #LEIvSCA pic.twitter.com/pW0WYOfJXx
— Leinster Rugby (@leinsterrugby) May 24, 2018
The Irishman missed Leinster’s semi-final win over Munster with a calf injury, that also affected his kicking during the Champions Cup final.
Now back and raring to go, he will be hungry to lead his province to their first Guinness PRO14 title since 2014.
With six appearances for the British & Irish Lions under his belt and Leinster’s record points scorer, a high-quality Sexton performance could be the difference in Dublin.
Guinness PRO14 Final 2018 Ticket Information: Prices start at just €50 at www.ticketmaster.ie with tickets available to suit every experience.
To book hospitality visit: https://www.pro14rugby.org/hospitality
For Travel packages visit: https://www.pro14rugby.org/travel-packages
For Fanzone & Dublin 7s visit: http://www.dublin7sfestival.ie