Ahead of this weekend's enthralling Heineken Cup encounters, Sky Sports assesses the eight teams aiming to succeed Leinster as champions.
Remember you can catch all of the action live on Sky Sports. Clermont against Montpellier gets us underway on Saturday on Sky Sports 1 HD (3.15pm), followed by Saracens' clash with Ulster at 6pm - with the match also available on Sky 3D.
On Sunday Harlequins against Munster will be on Sky Sports 2 HD from 1.30pm, with Leicester's visit to Toulon following at 4pm.
The Premiership champions are the top seeds going into the quarter-finals, however their domestic form of late will be a cause of concern. They have lost their last three Aviva Premiership games - going down to Exeter, Saracens and Gloucester - and although they did win the LV= Cup title in between, that only papers over the cracks that have appeared in their challenge. There is no doubting the potential at Quins, though, and if they can recapture their early season form they are a match for anyone. They won all six of their pool matches, scoring an impressive 28 tries along the way - although it can be argued that with Zebre, Connacht and Biarritz they had a more favourable draw than their rivals. There has been no such luck with the knockout stages with experienced Heineken Cup campaigners Munster the visitors in the last eight, while a trip to France against Clermont or Montpellier awaits in the semi-final. There is a wealth of talent available to Quins, including points machine Nick Evans and in-form England captain Chris Robshaw, while director of rugby Conor O'Shea is a clever tactician.
The Top 14 giants are the side to avoid in this season's competition - and have been in simply irresistible form. They have won five of their past six games domestically, while like Harlequins they negotiated their way through the Heineken Cup pool stages unbeaten. Unlike Quins, though, Clermont's pool was significantly tougher - and back-to-back wins over defending champions Leinster highlighted the threat they pose. They are currently the top try-scorers in the Top 14 with 66, while their defence is pretty special too, with the Auvergne defence being breached just 28 times. Morgan Parra has been in superb form with the boot, weighing in with 156 points in the league, while Napolioni Nalaga has powered over for 16 tries in all competitions. France internationals Wesley Fofana (10) and Jean-Marcellin Buttin (7) have also been scoring tries for fun. They also boast a sensational record at home, with their 66-21 rout of Agen stretching their unbeaten streak to 57 matches - meaning their quarter-final opponents Montpellier and potential last-four rivals Munster or Quins will not fancy a trip to the Stade Marcel Michelin.
When you can name a side that looks more like a World XV then you have to be respected. Jonny Wilkinson, Carl Hayman, Bakkies Botha, Simon Shaw, Matt Giteau, Juan Martin Fernandez Lobbe and Frederic Michalak... the Toulon squad is like a 'Who's Who of Rugby'. However, despite the galaxy of stars, Toulon have not enjoyed the success to justify the amount that has been spent. They were beaten finalists in the Amlin Challenge Cup in 2010 and 2012, while they were also edged out in last season's play-off for the French championship. The Top 14 leaders have high hopes of ending their 21-year wait for silverware this time around, though. Wilkinson's 20-point haul - taking the former England internationals tally to 329 in the league this season - provided the backbone to Toulon's 43-11 rout of Stade Francais as Toulon warmed up nicely for their Heineken Cup clash with Leicester. They have lost just once at Stade Felix Mayol in their past 18 games, meaning that home advantage against the Tigers will suit them in the last eight, however there is the daunting prospect of a possible trip to the in-form Saracens or Ulster in the semis.
The Aviva Premiership leaders have been timing their run of form to perfection. Sarries have won their previous five league encounters - including impressive wins over Leicester and Harlequins, while Wasps were brushed aside 22-13 last time out. Their never-say-die attitude makes them a dangerous proposition for any side, as their stunning 37-28 win over Racing Metro in Nantes proved. That victory helped Saracens claim top spot in the pool and a home quarter-final against Ulster. Saracens were in the same position last season but a tame loss to Clermont hurt them and there is a steely determination to avoid a repeat. Saracens' natural gameplan is not built around free-flowing rugby - they are the lowest try-scorers in the top eight, with Leicester crossing 14 more times than them - however with Owen Farrell and Charlie Hodgson they are able to punish any indiscretions, while they have the pack to batter their rivals into submission. They do have the talent out wide, though, should they switch to 'Plan B' with Chris Ashton, David Strettle and Alex Goode.
Having got the season off to a flying start with 13 successive wins in all competitions, Ulster's form has stuttered of late. Saturday's 22-18 win over Leinster in Dublin was their first in four attempts - however given they had last won away to their provincial rivals 14 years ago, they can head to Saracens with renewed hope of emulating last season's heroics. Ulster had carved their way through Europe before coming unstuck against Leinster in the final at Twickenham. Their form in the Heineken Cup this season has been equally impressive with five wins. They did lose to Northampton at Ravenhill - ending their unbeaten start to the season - but they responded with a historic win in Castres to clinch their place in the last eight. South African Ruan Pienaar continues to pull the strings at half-back, while Ireland fly-half Paddy Jackson is developing into a class act. Up front the pack will cause the majority of sides problems, with the likes of Chris Henry, John Afoa, Rory Best and Johann Muller.
Leicester will make the trip to Toulon full of confidence after their 36-8 demolition of Northampton at Franklin's Gardens. The Tigers are currently on a three-match winning run in the league and remain hot on the heels of table-topping Saracens. Their form in Europe this season has been equally impressive as they progressed from the hardest of the six pools. They beat Toulouse at a snow-covered Welford Road to claim their place in the last eight at the expense of their French rivals, while they also saw off the Ospreys and Treviso. The Tigers are five-time finalists of the competition but the last of their two wins came in 2002. However if they are to end their 11-year wait to lift the trophy again they will have to do it the hard way, with trips Toulon and then Saracens or Ulster now on the cards. Their forwards - with Dan Cole, Geoff Parling and Tom Croft to the fore - are a match for anyone on their day while powerhouse centre Manu Tuilagi and gifted fly-half Toby Flood means they have to be respected in the backs.
Montpellier return to Heineken Cup action as big outsiders to progress into the semi-final, let alone finish as champions. They claimed their place in the last eight as one of the two best runners-up - and that means they will have the unenviable prospect of tackling their compatriots Clermont at fortress Stade Marcel Michelin. Montpellier will be buoyed by back-to-back wins in the Top 14 while they did beat Clermont earlier in the season - although Clermont gained revenge on their own patch. Fabien Galthie's side have lacked consistency throughout an up-and-down campaign but they did win five of their pool games in Europe. The Georgian giant Mamuka Gorgodze is the man for the big occasions, while Johnnie Beattie will look to carry on his impressive form from the Six Nations. In the backs Francois Trinh-Duc, Matt Carrro, Shontayne Hape and Timoci Nagusa add some real quality - with Martin Bustos Moyano providing the points with the boot.
On paper, Munster have a mountain to climb if they are to make it past the quarter-final stage - however never write off the Thomond Park side. The former champions gatecrashed the last-eight places courtesy of their bonus-point win over Racing Metro on the final day. An added bonus for the Munstermen was the fact that they claimed the last 'best runners-up spot' at the expense of their old foes Leinster. Defeats to Racing and Saracens showed they are vulnerable away from home, though, while their form of late has hardly looked that of potential winners. They have won just once in their past five RaboDirect PRO12 outings, with their play-off hopes virtually ended after a 51-24 thumping against Glasgow Warriors the last time out. Donnacha Ryan, Peter O'Mahony and Conor Murray were notable absentees from Scotstoun, though, with one eye clearly on the trip to Harlequins. With Paul O'Connell back in action and Ronan O'Gara still a clas act, Munster will be hoping they can cause an upset.