Our latest preview ahead of the European Champions Cup looks at Pool 5, containing Toulon, Bath, Leinster and Wasps.
Champions Toulon will have to pull out all the stops as they face tough opposition against former winners Leinster and English heavyweights Bath and Wasps.
Let’s take a closer look at the teams.
Last season saw Bath making a return to European rugby’s main table and they delivered their most successful European campaign in six years as they reached the quarter-finals of the Rugby Champions Cup before losing narrowly to Leinster in Dublin.
Bath will be keen to improve on that showing this season and they definitely have the ability to do that as they have made some good signings.
The departure of Sam Burgess, after just one season in the 15-man game, has been offset by the recruitment of Scotland international back-row David Denton who is a destructive runner with ball in hand.
Amongst the backs, head coach Mike Ford has brought in Fiji scrum-half Niko Matawalu from Glasgow Warriors and Wales fly-half Rhys Priestland from the Scarlets as well as former London Irish utility back Tom Homer.
Amongst the regular campaigners, Springbok openside flanker Francois Louw will also be an important player, after several impressive displays at the Rugby World Cup while centre Kyle Eastmond will be highly motivated after missing out on selection to England's World Cup squad.
A big setback to Bath's campaign, however, was the pectoral injury sustained by Eastmond's midfield partner Jonathan Joseph during England's Rugby World Cup campaign.
Currently fifth in the Aviva Premiership, Bath kick off their campaign away to Toulon this weekend.
One to Watch: Niko Matawalu
The Fiji number nine joins the Recreation-based club after impressing during a three-spell with PRO12 champions Glasgow. Like most Fijian backs Matawalu is dangerous on the attack and don't be surprised if he unlocks opposing defences with some devastating runs.
The 2011 and 2012 champions will be determined to win Europe's premier cup competition again after disappointing campaigns, by their high standards, in recent years.
Last season, Leinster topped their Champions Cup pool to secure a home quarter-final against Bath before coming up short against Toulon after 100 minutes in Marseille in the semi-final.
A fifth-placed position in the PRO12 secured Champions Cup rugby for the 2015/16 but Leinster's inconsistent form in the PRO12 saw them finish outside the play-off positions in that competition.
That led to the Irish province parting ways with head coach Matt O'Connor with former Leinster captain and forwards coach Leo Cullen taking over the reins.
Another stalwart Isa Nacewa has returned to Leinster after coming out of retirement and will captain the Irish province this season. Nacewa, who retired in 2013, is joined by Ireland fly-half Jonathan Sexton and Blues lock Hayden Triggs as the club's major signings.
Experienced heads like Jamie Heaslip, Cian Healy and Sean O'Brien will be at the forefront of the forward effort while Fergus McFadden, Luke Fitzgerald and the Kearney brothers – Rob and Dave Kearney – should lead the charge from the back although Rob Kearney is battling a hamstring injury and is doubtful for Leinster's Champions Cup opener against Wasps at the RDS Arena in Dublin on Sunday.
One to Watch: Jonathan Sexton
Ireland's first-choice number 10 returns to his old stomping ground after spending a couple of seasons with Top 14 outfit Racing Metro. A groin injury wreaked havoc with his World Cup campaign which means he will be keen to impress in the Champions Cup when fully fit.
After being crowned champions in 2013, 2014 and 2015, Toulon face arguably their toughest challenge in Europe's premier cup competition this season.
There's a big rebuilding project currently underway at the Stade Felix Mayol-based club as the end of the 2015 season saw the departure of stalwarts – and bona fide legends of the modern game – Carl Hayman, Bakkies Botha and Ali Williams, who have all retired, as well as Chris Masoe who has moved to Racing 92.
Paul O'Connell was brought in to replace Botha and Williams in the second row along with Duane Vermeulen and Samu Manoa to bolster the pack but O'Connell's torn hamstring, sustained at the World Cup, means he will effectively miss the entire campaign.
Toulon are also set for a change in their coaching structure with head coach Bernard Laporte set to hand over the reins to Diego Dominguez in January.
Matt Giteau will once again be expected to provide the spark to unleash explosive backs like Mathieu Bastareaud, new signing Ma'a Nonu and proven finishers like Bryan Habana and Drew Mitchell, but Giteau's burden will be made lighter by another new recruit, fellow Wallaby Quade Cooper.
Keep and eye on Vermeulen and Manoa, who are both strong ball-carriers, while Steffon Armitage has proven over the past couple of seasons that he is one of the game's best operators at the breakdown and a handy option with ball in hand.
One to Watch: Quade Cooper
He will be keen to prove that he can still cut it on the big stage, after featuring in just one of the Wallabies' seven matches during their recent Rugby World Cup campaign. Cooper in top form is a joy to watch and he will be expected o bring out the best in his outside backs with his playmaking abilities.
Wasps qualified for the Champions Cup after finishing in sixth position in the Premiership during the 2014/15 season.
Last season, they were one of the tournament's surprise packages and reached the quarter-finals where they were beaten by eventual champions Toulon.
Despite having a new home venue, the Ricoh Arena in Coventry – where they have performed well – and signing quality players like All Blacks backline duo Frank Halai and Charles Piutau as well as Wallaby great George Smith, the 2004 and 2007 champions will be the underdogs in this pool based on current form.
Wasps are currently in eighth position in Aviva Premiership with two wins and two defeats from their four opening matches, although they head in to their opening Champions Cup clash after claiming a 23-3 home win over Gloucester.
They should provide stern opposition in Coventry but it will be much more difficult when they away from home, which will make it tough for them to progress to the knockout stages again this season.
Director of rugby Dai Young did well to secure the services of Halai, Smith and especially Piutau who was unlucky not to make the All Blacks' World Cup squad.
Wasps' opener against Leinster could play an important role in how they fare during the rest of the tournament. The two sides also faced off during the pool stages last season with Leinster winning narrowly in Dublin and the teams drawing at the Ricoh Arena.
Wasps will do well if they can get a repeat of the latter result this weekend.
One to Watch: George Smith
One of the best openside flankers in the modern era, Smith has been there and done it all in the game and even though he is 35 years old, he is still at the top of his game. Smith's prowess at the breakdown is his well known but he has shown in Wasps' Premiership campaign that there's nothing wrong with his al-lround game.