Saracens are hoping to crack the 80,000 barrier for their home Aviva Premiership clash with Harlequins at Wembley Stadium, while reigning Heineken Cup champions Leinster Rugby travel to Limerick to face Munster Rugby in a 1st v 2nd RaboDirect PRO12 meeting at a sold-out Thomond Park.

Edinburgh Rugby are up against the Scarlets in another European dry run at Murrayfield before their historic meeting with Toulouse who have to warm-up for their trip to the Scottish capital with a Top 14 clash against Stade Francais Paris which is likely to attract over 70,000 spectators to the Stade de France.

There were a few nerves about as the Heineken Cup quarter-finalists began the build-up to their knockout assignments on the weekend of 7/8 April with the reigning champions Leinster among four clubs in the last eight to lose.

In fact, Leinster went down 23-22 at home to the Ospreys in a defeat that ended a 20-match unbeaten run, albeit without 10 of their leading international players.

Their build-up to a near sell-out clash with Cardiff Blues at the Aviva Stadium on Saturday, 7 April, will move up to another level this weekend when they travel to Limerick for a top of the RaboDirect PRO12 table meeting with arch-rivals Munster.

Brian O'Driscoll made his long awaited return to action against the Ospreys following surgery in the wake of the World Cup, while New Zealand World Cup winner Brad Thorn joined fit-again skipper Leo Cullen in the second row. All three will be available to take on the Blues, Thorn having been added to the Leinster squad for the Heineken Cup knockout stages.

The Blues were beaten 26-14 at home by the Scarlets and learned over the weekend they will be without Wales' Grand Slam winning skipper Sam Warburton for six weeks because of the shoulder injury he picked up against France.

With 99-times capped Martyn Williams also struggling with a rib cartilage injury, the Welsh region have a few back row issues to resolve before they head to Dublin.

Jamie Roberts, Leigh Halfpenny, Bradley Davies and Gethin Jenkins are all due to return for their trip to high-flying Glasgow Warriors on Friday night, but skipper Paul Tito is struggling with a head injury he suffered three weeks ago in Treviso.

Top seeds Munster Rugby had a Tommy O'Donnell try to thank for their 20-16 victory in Galway over Connacht Rugby last weekend and were delighted to see back row stalwart David Wallace successfully negotiate his second game since returning to fitness following knee surgery. The 35-year-old will be keen to add to his 85 Heineken Cup appearances when Munster host Ulster Rugby on Sunday, 8 April and try to make up for lost time this season by featuring in a fifth final.

Ulster welcomed back skipper Johann Muller for the first time since Round 6 of the Heineken Cup in last weekend's hard earned victory over Benetton Treviso. Their final outing before heading south to Limerick next month will be another 'Italian Job' at Ravenhill on Friday night when they host Aironi Rugby.

Edinburgh Rugby, who have sold more than 25,000 tickets for the first Heineken Cup quarter-final on Scottish soil, against Toulouse at Murrayfield on Saturday, 7 April, were beaten 29-15 at home by the Dragons last weekend and have another Welsh assignment this weekend when they take on Amlin Challenge Cup quarter-finalists the Scarlets at home in a vital European dress rehearsal.

Head Coach Michael Bradley will have his Scottish internationals back for that game, as will his Toulouse counterpart Guy Noves when his side tries to stay ahead of the chasing pack in the Top 14 when they continue their quarter-final countdown with a trip to Stade de France on Saturday night to meet Stade Francais Paris.

That will make it two international venues in a row when they head to Murrayfield and IRB World Player of the Year Thierry Dusautoir will be back to lead his side into both games after resting for a week following the 2012 RBS 6 Nations.

Toulouse were beaten 18-17 at Bordeaux-Begles last weekend and that defeat allowed ASM Clermont Auvergne to cut the gap at the top of the Top 14 to a single point thanks to their 29-23 home win over Perpignan. Outside half David Skrela was the home hero as he kicked eight penalties for a match-winning haul of 24 points.

Clermont, who have to travel to English champions Saracens on Sunday, 8 April, head to Biarritz Olympique for their final outing before they try to make it fourth time lucky in a Heineken Cup quarter-final.

Skipper Aurelien Rougerie and fellow French internationals Welsey Fofana and Julien Bonnaire will all be available for selection this weekend ahead of the Vicarage Road contest.

Saracens, meanwhile, are another of the Heineken Cup quarter-finalists who will be warming-up for their big day with a game at an international venue. In their case it is a top of the Aviva Premiership clash with London rivals Harlequins at Wembley Stadium on Saturday.

Their five try, 45-9 triumph at Sale Sharks last weekend moved them ahead of Quins on Friday night, but they didn't stay on top for long as the Amlin Challenge Cup holders and quarter-finalists beat Bath Rugby 14-6.