Round 4 sees the reverse fixtures of last week's matches, as Leicester, Edinburgh and others look to turn around last weekend's results to keep their prospects of reaching the quarter finals alive.
Munster Rugby v Scarlets
After an incredibly close encounter in Llanelli last week, the Scarlets have the unenviable task of travelling to Thomond Park to keep their hopes of topping Pool 1 alive. The Welsh side's chances will be markedly improved by the news that George North will be fit for the reverse clash, after missing out on last week's fixture at Parc y Scarlets.
Despite defeat at home, and having not beaten Munster in the last 13 games, the Scarlets will have belief that they can pull off another famous victory after their performance in the second round at Northampton.
Munster are without Doug Howlett, who is out for the rest of the season, but Irish international Keith Earls could be ready to return to the squad after recovering from a knee injury. The Irish province will be wary of the Scarlets threat on the road, and considering how close Northampton came to victory in Limerick, the Scarlets can't be ruled out. As ever, Ronan O'Gara could be the difference between the sides. Munster by less than 7.
Northampton Saints v Castres Olympique
Following a third defeat out of three, last season's finalists Northampton are all but out of the competition. They were always going to struggle to stay in contention with a win in France, but the heavy nature of the defeat will have hurt.
While their chances of qualification are gone, Jim Mallinder has stated that the Heineken Cup is still important to his side, and the Saints will be out to win their remaining three matches in order to keep up the momentum of their Premiership charge.
Despite defeat in their first two games, Castres are not out of the competition yet, although they will need to win every game and hope that both the Scarlets and Munster trip up along the way. They will also find it tough going at Franklins Gardens, Northampton are not likely to repeat their dismal performance against the Scarlets when the French side visit this weekend. Northampton by more than 5.
Edinburgh Rugby v Cardiff Blues
Gavin Henson may be in line to make his debut for the Cardiff Blues in a crunch match in Pool 2. Following curtailed appearances for first Saracens, and then big-spending Toulon the Welsh international returns to his home nation, and finally looks to have recovered from a wrist injury that has kept him out since August. After a perfect start to their Heineken Cup campaign so far, the Blues will face a tough challenge as they travel to Edinburgh. The Welsh side will still be without Martyn Williams but have no fresh injury worries.
Edinburgh will be disappointed not to have picked up a losing bonus point in Cardiff last week after a good start to the competition themselves. A win on Friday night would see them leapfrog Cardiff at the top of the table, and with home advantage, the Scots will be hopeful of a third victory of the season.
London Irish v Racing Metro 92
London Irish picked up their first victory of this season's Heineken Cup in Paris last week with their thrilling bonus point victory over Racing Metro. The win keeps their hopes of progressing to the quarter finals alive, and Irish will welcome the Parisians to the Madejski Stadium confident of picking up back-to-back victories against Racing. Irish Number 8 Chris Hala'ufia will be able to play, despite being cited for a dangerous tackle on Racing Metro full-back Gaetan Germain in last week's fixture, and the London side have no new injury concerns heading into the weekend.
Racing have faltered a little in recent games, after being humbed in the Paris derby in the Top 14, they then shipped over 40 points at home last weekend. Travelling to Reading will not be an easy task for the Parisians, who have now conceded over 40 points in each of their last two Heineken Cup matches. London Irish by less than 7.
Montpellier v Glasgow Warriors
Montpellier will wonder how they have failed to secure a victory so far this season. After a thrilling draw against Leinster and a close defeat to Bath, the French side were five points adrift of Glasgow at Firhill last weekend.
Glasgow head into Saturday's fixture in second place, three points behind leaders Leinster. They will be disappointed by their lapse of concentration that allowed Montpellier to earn a bonus point last weekend, and coach Sean Lineen understands that his side cannot afford to be so slack on their travels if they are to keep up the pressure on Leinster at the top of Pool 3.
Leinster Rugby v Bath Rugby
Leinster will hope to be far more clinical on Saturday than last week's match at the Rec which saw the champions butcher three easy try-scoring opportunities. Victory put them clear at the top of a tight Pool 3, and a win in Dublin this weekend will ensure that they are all but through to the quarter finals with two more games to spare.
Bath played like a side possessed as they seemed to sweep aside the poor form that had seen them lose three Premiership games on the bounce to take the fight to Leinster. The West Country side were 14 minutes away from a famous victory before Francois Louw suffered a rush of blood to the head, after an inspired performance as captain. It will be an even tougher ask for Bath to win in Dublin to keep them in contention for qualification, but if they can play the same intense on-the-gain-line rugby that battered Leinster last weekend, they have every chance of causing an even bigger upset in the Irish capital. Leinster by 7.
Leicester Tigers v Clermont Auvergne
Leicester were never going to go to the Parc des Sports Marcel Michelin and be given an easy ride “ the French side haven't lost at home since 2009 “ but the 18 point margin of the defeat will have disappointed Richard Cockerill. It was ill-discipline rather than difference in quality that decided the outcome, and Leicester will have to keep their tempers in check at Welford Road if they are to turn over Clermont in round 4.
Clermont will have to do without Georgian prop Davit Zirakashvili, who will miss the rest of the pool stages with a fractured arm sustained over the French side's victory over Leicester last week.
The Tigers sit third in Pool 3, but with just two points separating themselves at leaders Clermont, the pool is far from over. After a shocking start to the season at home, Leicester are finally rebuilding fort Welford Road, and should have the quality and tenacity to see off Clermont on Saturday. Leicester by less than 7.
Aironi Rugby v Ulster Rugby
Aironi are still chasing their first points of the competition, without even a losing bonus point to their name. They will find It a tough ask, considering the current form of their visitors on Saturday.
Ulster still stand a realistic chance of qualification in a tough pool, just a point behind leaders Clermont. Their try bonus point last week was crucial, and although they will find it tougher to repeat the task at the Stadio Brianteo, it can put them in a strong position with their two rivals clashing in Leicester. Ulster by about 7.
Ospreys v Saracens
Saracens victory over Ospreys at Wembley last week put the London club at the top of Pool 5, three points clear of Biarritz and their hosts for the weekend, Ospreys. After being pushed all the way to the end by the Welsh region, the Aviva Premiership champions are in for an even tougher challenge in South Wales this weekend.
Their hosts will hope to welcome back Welsh international prop Paul James, injured since the World Cup, and scrum-half Kahn Fotuali'I as their injury list gradually decreases, returning the Ospreys to full strength. They will also be boosted by the news that centre Ashley Beck, who scored twice for the Ospreys last weekend, has signed a new contract with the club keeping him in Swansea until 2014.
One thing the Welsh region will hope to increase is their attendance, which has averaged just over 6,000 this season, compared to the blockbusting 40,000 present at Wembley for the reverse fixture last weekend. The Ospreys will want to create a more hostile environment to welcome the group leaders, as they attempt to return to the top of Pool 5 and keep themselves in a strong position to reach the quarter finals. Ospreys by about 3.
Biarritz Olympique v Benetton Treviso
Entering their second season In the Celtic League, Treviso have been a real success story for Italian rugby, and they have continued to show this in this season's Heineken Cup. Although qualification for the quarter finals is little more than a distant dream, the Italians are just four points behind leaders Saracens after their stunning victory over Biarritz last weekend.
Although the French basement club are struggling terribly this season, defeat at home to Treviso would be absolutely unthinkable. The Basque side are still very much in contention “ their victory over Saracens last time out at the Parc des Sports Aguilera showed this “ but defeat in Italy last week is a major setback, and it may even be in the best interests for Biarritz to concentrate on survival in the Top 14 this season. That said, their squad has talent that Treviso can only dream of, and victory should go to Biarritz this weekend. Biarritz by less than 7.
Gloucester Rugby v Connacht
Gloucester's tight victory in Galway was just their second in their last eight matches, but it would be unfair to take away from the Irish minnows performance. They have so far made life difficult for the sides visiting the Sportsground, whilst still in search of their maiden Heineken Cup victory.
Gloucester are another side whose chances of qualification are incredibly slim, especially given the two sides above them in the table. They will however keep on fighting, and should see off the Connacht challenge fairly comfortably at Kingsholm, in spite of their current slump. Gloucester by more than 7.
Toulouse v Harlequins
Harlequins couldn't quite live up to their toughest test, as their 14 match unbeaten run was ended by the French champions last week. They now face the even tougher challenge of travelling to the south of France, needing a victory if they want any chance of topping the group.
If anything, last week's defeat will have made Saturday's game easier on the Premiership leaders. Gone is the pressure and spotlight on Quins to continue their unbeaten run, and they have the chance to enjoy their rugby without that monkey on their shoulders anymore.
Toulouse will still prove a stern challenge, especially in the intimidating confines of the Stade Ernest-Wallon, and the French giants will be looking to make it five wins out of five against Harlequins. A victory would put them eight points clear at the top of the group, an unassailable lead “ Quins therefore know they will have to try and hang onto the coattails of Toulouse and grab at least a bonus point victory to put them in a good position to take one of the top runners-up spots into the quarter finals.
It will be tough for Quins, especially given the massive psychological blow Toulouse's dominance all around the park at the Stoop last week, and despite the quality pairing of Danny Care and Nick Evans at half back, their opposite numbers Luke Burgess and Luke McAlister are possibly the best 9/10 pairing in European rugby at the moment. Toulouse by about 7.