Saracens went top of the Pool after they clinched a vital victory in their return game against Munster to put themselves in the driving seat for a quarter-final place.
The Londoners suffered a 15-9 defeat in the first game between the two sides but managed a vital losing bonus point at Thomond Park to keep their Heineken Cup hopes alive.
Saracen Owen Farrell and Ronan O'Gara of Munster enjoyed a rare old kicking duel with Farrell putting his nightmare performance in the first leg behind him to clinch a vital 19-13 win - their first against the former double champions.
Munster did manage a losing bonus point at Watford and the qualification race looks like it will go right down to the wire with three teams who can still qualify for the last eight of the tournament.
Saracens' win means that they, Munster and French side Racing Metro 92 are all still fighting for a lucrative quarter-final place with two rounds in the Pool stages to play.
Racing may be in second place and only two points behind Saracens in the Pool but the French side probably have the hardest run-in in the final two games, with a trip to Munster and a clash with Saracens.
The French side completed their own double over last season's semi-finalists Edinburgh with their 19-9 victory in the second leg between the two sides at Murrayfield.
Edinburgh, who stunned everybody by reaching the last four of the tournament last season, haven't come close to the knockout stages and still have yet to record a win, a try or any match points.
