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Unbeaten Munster need a bonus point victory at home over Castres Olympique to guarantee top spot. A bonus point triumph would take them to 23 points, which is the most the Scarlets in second place can achieve over the final two rounds. Munster have beaten the Scarlets in both Pool matches and would therefore go ahead of them on the head-to-head basis. A straightforward win for Munster, and any form of defeat for Scarlets, would also guarantee a 13th quarter-final.
Pool 2
Wide open with Edinburgh Rugby and Cardiff Blues neck and neck on 13 points and London Irish still in contention with matches against the top two to come.
Pool 3
Any kind of win for Leinster Rugby over Glasgow Warriors at Firhill will be enough to guarantee the reigning champions safe passage into the last eight. The only other unbeaten club along with Munster Rugby - they opened with a draw in Montpellier - Leo Cullen's men have a six point lead over their Scottish hosts going into Round 5.
Pool 4
Too close to call with three major clubs still in the hunt. Ulster Rugby go into the final two rounds with a two point lead over Leicester Tigers against whom they incurred their only defeat in the Pool to date. Tigers have ASM Clermont Auvergne one point behind them on 11. Ravenhill will host one of the key battles in Round 5 when Ulster meet the Tigers, while ASM travel to Aironi Rugby before hosting Ulster in Round 6.
Pool 5
Saracens could win their Pool with a game to go if they can clinch a bonus point victory at Vicarage Road over Biarritz Olympique and prevent the French club from earning a point. That would take Saracens to 19 points and a guaranteed place in the quarter-finals. However, an away win for Biarritz would open up the Pool for a mad scramble in Round 6, when Ospreys travel to France and Saracens head to Italy to face Benetton Treviso.
Pool 6
The battle between four-times champions Toulouse and reigning Amlin Challenge Cup holders Harlequins looks destined to run to Round 6. Toulouse lead Quins by a point in the head-to-head stakes over their two Pool matches and also lead the Pool by a point. They host Connacht Rugby in Round 5 before heading to Gloucester in Round 6. Quins host Gloucester Rugby, who are still in the mix with nine points in third place, next weekend before ending with a trip to Galway to face Connacht.
