Pool 4 has a very familiar look to it this year as Munster, Leicester and Racing are drawn together again, and this time are joined by Castres.
Teams: Leicester Tigers, Munster, Racing 92, Castres
It's the third such year in succession that the Tigers and Munster lock horns in the pool stages, and the second in which Racing join the past champions. Who can take advantage of their familiarity this year?
Leicester
Champions Cup record: P144 W92 D5 L47
Best finish: Champions (2000/01, 2001/02)
What's hot: New signings George Ford, Jonny May and Dominic Ryan have all settled well at the club. Four wins from their first six is a strong start to the campaign, with eye-catching victories over Exeter, Quins and Bath. Their form at Welford Road is also a thing to behold, with defeats there in Europe extremely rare.
What's not: While recruitment has been solid, the Tigers also lost some key men before the season started. Owen Williams, Lachlan McCaffrey, Ed Slater, Peter Betham and Freddie Burns will all be missed. JP Pietersen also jumped ship to Toulon after one injury-ravaged campaign. Manu Tuilagi's knee injury is also a major blow.
What's changed: Matt O'Connor embarks on his first full season in charge, while there has been a lot of change to the squad with 13 incomings and 11 exits.
Key player: Ben Youngs
Munster
Champions Cup record: P158 W109 D1 L48
Best finish: Champions (2005/06, 2007/08)
What's hot: Munster made a return to the business end of Europe last season charging to the European Cup semi-finals, and the majority of that squad has remained. The signings of Chris Farrell and JJ Hanrahan look shrewd, while incoming flanker Chris Cloete looks a marvellous capture.
What's not: A gluttony of injuries to the second row has badly affected their start to the season and all involved at Munster will be hoping Jean Kleyn is fit for their opener against Castres on Sunday. Centre Jaco Taute's serious knee injury is also a hammer blow to the side. Tyler Bleyendaal and Ian Keatley have proved too inconsistent at fly-half thus far. The ongoing uncertainty over the head coach position with Rassie Erasmus set to depart in December is also far from ideal.
What's changed: Stalwart Donnacha Ryan departed to Racing 92, fellow lock Dave Foley joined Pau, while the creative spark of Francis Saili left to Harlequins. Seven players were signed, but the biggest change occurred over the summer when news broke that Erasmus and key defensive coach Jacques Nienaber gave notice of their plans to exercise the release clause in their IRFU contracts and return to the Springbok set-up.
Key player: Conor Murray
Racing 92
Champions Cup record: P46 W19 D3 L24
Best finish: Runners-up (2015/16)
What's hot: Racing's squad is up there with the best in the competition and after last year's failings they will be ultra-determined to challenge again. Pat Lambie looks a super signing provided he can avoid injury, albeit he won't arrive until November. Fellow incomings Virimi Vakatawa, Donnacha Ryan and Census Johnston will all improve the squad. If Carter, Machenaud, Imhoff et al click, they could be one of the favourites.
What's not: A strong start to the season has fizzled out somewhat with three wins from their first four followed by three losses on the bounce heading into Europe. Consistency of performance and stamina over 80 minutes would appear the major weaknesses. The departure of Chris Masoe is also a loss from a leadership point of view.
What's changed: Not a whole lot off the field in truth, though the two Laurent's and Ronan O'Gara will hope for vastly different performances on the pitch. The biggest potential change of all did not come to fruition of course, with the prospective merger (or takeover depending on your view...) with (or of) Stade Francais thrown out after protests from the Stade players.
Key player: Dan Carter
Castres
Champions Cup record: P76 W27 D2 L47
Best finish: Semi-final (2001/02)
What's hot: As is the case with many French teams, Castres appear to be a vastly different animal at the Stade Pierre Fabre than they are away from home. In last season's Champions Cup for example, they beat Montpellier and Northampton at home and drew with eventual semi-finalists Leinster, in a match they should really have won. Sides will do well to go there and win. Supremely talented winger David Smith is also seriously difficult to handle.
What's not: Perhaps the outsiders in a tough group, Castres will be up against it to progress. Their squad is quite lightweight and the key will be whether their forwards are up to the task of travelling to Thomond Park and Welford Road and matching the intensity and physicality, both at the set-piece and in the loose.
What's changed: Wingers Remy Grosso and Horacio Agulla left to Clermont and back to Argentina respectively, while brilliant scrum-half Antoine Dupont exited to Toulouse, all of which are negatives. Ludovic Radosavljevic has arrived from Clermont though, and could prove a decent signing.
Key player: David Smith