Harlequins guaranteed a home quarter-final after winning their first five pool matches, while ASM Clermont Auvergne, Ulster and Toulon are also already guaranteed places in the last eight and are now playing for ranking places and the chance to gain home advantage in the quarter-finals.
Leicester and Toulouse are joined by Biarritz, Castres, Leinster, Montpellier, Munster, Northampton Saints, Racing Metro and Saracens are in contention for the remaining places in the last eight or qualification for the Amlin Challenge Cup quarter-finals.
ERC European ranking points are also at stake throughout the pool and knockout stages. A pool winner is guaranteed four ranking points, and a runner-up three points. Two points are awarded to a club which finishes third, and one point to a club finishing fourth. Tier positions in the 2013/14 Heineken Cup pool draw for qualified clubs will be determined by the ranking points system.
The quarter-final line-up will be confirmed at the conclusion of the atch action in Round 6 on Sunday, with the semi-final draw performed in the TV studio at Welford Road.
Click here for the pool tables.
Here are some pointers for this weekend:
Pool 1
Victory for Saracens over Edinburgh on Sunday would see them confirmed as Pool 1 winners.
Munster have to defeat Racing Metro at Thomond Park and hope that Saracens lose to Edinburgh in order to top the pool.
If Munster and Saracens both win, then Munster need results elsewhere to go in their favour if they’re to emerge as one of the two best runners-up.
Racing Metro are still mathematically in the equation, but they would need a bonus-point win in Limerick as well results elsewhere to secure a best runners-up spot.
Pool 2
It’s all about Leicester Tigers and Toulouse at Welford Road. A win for either would settle the pool and earn a place in the last eight.
Defeat for Toulouse could still see them in contention for a best runners-up place.
Defeat for Leicester could leave them in contention for Amlin Challenge Cup qualification.
Pool 3
Win, lose or draw at Biarritz on Friday evening, Harlequins were already guaranteed a home quarter-final and vying with ASM Clermont Auvergne and Toulon for the top ranking of the eight qualifiers.
Pool 4
Already sure of a spot in the last eight, Ulster go to Castres in search of a first Heineken Cup win on French soil. Victory could ensure a home quarter-final, depending on results elsewhere, while defeat would see them on the road in the knockout stage.
Northampton Saints travel to Glasgow Warriors in contention for a best runners-up place and for qualification for the Amlin Challenge Cup.
Castres would need a lot of favourable results to book a best runners-up spot. But if they defeat Ulster, the Amlin Challenge Cup is on the radar.
Pool 5
Even a point at Scarlets would almost certainly give ASM Clermont Auvergne a home quarter-final at fortress Stade Marcel Michelin.
Leinster go to Exeter Chiefs chasing a best runners-up place. A win is the minimum requirement for the defending champions, while five points will probably be needed as well as favourable results elsewhere.
Pool 6
A losing bonus point at Montpellier will be enough to secure Toulon a home quarter-final, but a home win for Montpellier in the all-French clash would drastically change the landscape for the best runners-up places. This fixture has a huge role to play in the overall shape of the qualification places and draw.
