Holders Leinster lead an Irish charge in this weekend\'s European Cup quarter-finals, with French heavyweights Toulouse and Clermont facing tricky away trips to Edinburgh and Saracens respectively. In a swing away from Six Nations form, Grand Slam winners Wales are represented by just one club, Cardiff Blues, while Leinster are joined in the last eight by provincial rivals Munster and Ulster, who play each other on Sunday. Fresh from a 31-3 Celtic League thrashing by Glasgow, the sacking of Gavin Henson for drunken behaviour on the flight home and news that Jamie Roberts will be out for six months with injury, Cardiff travel to play Leinster as massive underdogs. The Irish province, two-time champions in Europe, have been boosted by the return to the team of Ireland captin Brian O\'Driscoll, with World Cup-winning All Black Brad Thorn also in line to provide some beef up front. \"A last-eight game this weekend is exactly the tonic I need after five months out,\" said O\'Driscoll, who underwent surgery for a trapped nerve in his shoulder. \"Finally having a couple of games under my belt it feels good to be back and you forget what it was like on those lonely Saturdays when you\'re sitting at home when everyone else is out playing games after a week\'s hard training.\" He added: \"If anything, we have to up our standard, because when you get to the knock-out phase of European rugby, only the best sides go on to the semis and final so we have to make sure we\'re that side.\" Cardiff coach Justin Burnell admitted that his side, who will also be missing influential Kiwi lock Paul Tito (migraines after concussion), Rhys Thomas and Fau Filise (shoulder), were rank outsiders. \"Nobody is going to expect us to go there and win,\" he said. \"Rightly so, everybody will write us off, which in all fairness, is quite nice for us because there will be no pressure. \"If we go there, give it our all and if we come away with a good performance and a good result it will be totally unexpected.\" English champions Saracens host Clermont at Vicarage Road on Sunday, just a week after setting a world club attendance record in the Premiership at Wembley in a narrow defeat by pace-setters Harlequins. Saracens suffered a woeful campaign in Europe last year, when they finished bottom of their pool with five defeats out of six games, but coach Mark McCall said his team had benefitted from playing at a more intense level. \"We regrouped really well after last season\'s final pool match and we went unbeaten for the rest of the season (to win the Premiership),\" said McCall. \"Clermont have got a lot of good players and will bring a real intensity to the game. They see themselves as title contenders. \"These opportunities of getting a home quarter-final don\'t come along too often and it\'s important we seize the moment.\" Scotland performed miserably in the Six Nations, taking home the wooden spoon after losing all their games, and Edinburgh\'s form in the Celtic League has been similarly poor, sitting second from bottom with just five wins in 19 outings. But the capital\'s team has bucked the formbook come European rugby, with double pool triumphs over Racing Metro and London Irish helping them secure home advantage against four-time champions Toulouse. \"As long as we turn up we can match any team on our day,\" said Edinburgh captain Greig Laidlaw. \"Going into the Heineken games there has been a huge sense of belief and a great build-up.\" With what will be a Scottish club record of more than 30,000 fans in the Murrayfield stands, Laidlaw added: \"This is probably the biggest game ever for the club. We\'re going in looking to win and give it our best shot.\"