The Dubliners are eight points adrift of Pool 5 leaders ASM Clermont Auvergne, who are many people's favourites to finally lift the biggest prize in European club rugby, and need a bonus-point victory over the Scarlets.
But the Irish province, who have won three out of the last four Heineken Cup finals, are facing being knocked out of the Pool stages of the tournament for the first time since 2008.
Leinster have only missed out on the knock-out stages twice in the last nine seasons, but they are facing a Scarlets side which has seen its form dip dramatically in recent weeks.
The Welsh side, who have slipped out of the top four play-off places in the Pro12 for the first time this season, are still looking for their first win of their European campaign.
- Leinster have triumphed in their last three Heineken Cup meetings with Scarlets, though Scarlets did grab a losing bonus point in their match earlier this season.
- Leinster have turned over the least amount of ball (10 conceded per game) this season and have retained possession at a competition high 97% of rucks and mauls.
- Leinster's Jamie Heaslip has completed the most tackles without missing any, boasting a 100% success rate by making 50 in four appearances.
- Jonathan Sexton, Leinster's top points-scorer in this tournament, could reach 400 for the province if he scores 13 points this weekend.
- The Welsh side are on a run of four consecutive defeats in this competition and have seven losses in their last eight.