The Heineken Champions Cup - as it's called now, in an amalgam of the old and new names - kicks off this weekend and, acknowledging that you may not have kept abreast of goings on in English and French club rugby, here's our pool by pool guide briefing sketching out the contenders. 

Pool 1

By several miles the most decorated pool in this year's competition, with the four sides boasting a combined total of 11 European Cups between them since the inaugural one in 1996.  

Leinster will have to cope without the retired Isa Nacewa, the veteran full-back who remained a pivotal presence right to the end, nailing the late penalty which won the province their fourth European title in May.

They won't have the flashy talents of Joey Carbery to call upon this year though they are otherwise fairly well served in the out-half position. 

Last year, they became the first team to win both the European Cup and the Pro14 (in any of its manifestations) in the one season and maintaining the same hunger and ruthlessness will be an important challenge for Leo Cullen and Stuart Lancaster. Still, they remain clear pool favourites.   

Full Champions Cup fixtures here

Wasps have made a healthy start to the new Premiership season, albeit they are heading into their daunting European opener off the back of a 35-21 home defeat against Gloucester. 

International No 8 Nathan Hughes was cited for an apparent punch late in the game and will miss the Leinster match after the disciplinary hearing was delayed - much to his chagrin. 

The last English outfit outside of Saracens to win the European Cup, Wasps have a strong pedigree in the competition but narrowly missed out on escaping the pool phase last year. 

Kiwi fly-half Lima Sopoaga, signed from Southland in the summer, has made an impressive start to life for Wasps and starts at 10 on Friday against Leinster. 

Johnny Sexton in action against Wasps in 2017

The Toulouse name doesn't carry the same fear factor it did back in the nineties and noughties. The historic aristocrats of French and European rugby failed to even arrive at the starting blocks for last year's Champions Cup, the first time ever they failed to qualify for the competition. 

However, they re-grouped last year and jumped seven places in the Top 14, finishing 3rd in the regular season and easily booking their spot in the top tier European competition. 

One of their hottest prospects in the silky out-half/centre Romain Ntamack, son of the former French international Emile Ntamack.

Yoann Huget and Maxime Medard are key figures in the backline while another French international, Maxime Mermoz joined the club from the Newcastle Falcons in the summer. 

Jerome Kaino, Richie Gray and Leonardo Ghiradlini are standout members of the international contingent. 

The Recreation Ground last weekend for Bath's meeting with the Exeter Chiefs

The 1998 champions qualified by virtue of a sixth place finish in last year's Gallagher Premiership. Aside from a narrow quarter-final loss to Leinster in 2015, Bath have continually failed to progress past the pool stage in the past decade. 

Todd Blackadder's side have had a mediocre start to the new Premiership season as their powerful back-line figures of Anthony Watson and Jonathan Joseph are both absent through injury.  

New signing Jamie Roberts, who joined from Harlequins in the summer, is also laid low with a fractured cheekbone. Bath lost 39-24 at home to high-flying Exeter last weekend. 

Sixth place finishers in last year's Premiership, they are unlikely to progress. Will it be a case of Blackadder Comes Fourth?

Pool 2

Theoretically, the Top 14 champions should be formidable opponents in Europe but Castres have continually demonstrated over the years that their priorities lie at home. 

The club has no love for the competition. Only once in 14 attempts have they escaped the pool phase. There's no reason to think they'll be any more successful this time. 

Coach Christophe Urios has added Scott Spedding to the side that won last year's Top 14 after squeezing into the playoffs in sixth place. 

Dungannon born out-half Gareth Steenson is a forgotten man in his own land but he has been a central figure in Exeter Chiefs' rise to prominence in recent years. 

Exeter won the Premiership in dramatic circumstances in 2016-17, beating Wasps 23-20 after extra-time in Twickenham. They fell at the final hurdle when trying to repeat the triumph last year.

Sam Simmonds is out of action with an ACL injury but they're coping well, winning six from six and sitting top of the Premiership early on. 

Munster's Joey Carbery in action against Ulster

There's a curious air of novelty around Munster this season thanks to the arrival of Joey Carbery, generally presumed to be the least Munster-ish out-half in the history of Munster (though old-timers might point out that Tony Ward is remembered for creative elusiveness). 

The Carbery arrival and the promising start to the season, underlined by the performances against Ulster and Leinster, have generated plenty of excitement around the place. 

Tadhg Beirne is another strong addition. The Kildare player's switch to Scarlets saw a spectacular ressurection of his professional career and the 2016-17 European player of the year contender has made a highly promising beginning to life in Limerick and scored their opening try against Leinster at the Aviva on Saturday. 

Peter O'Mahony made it clear last year he was heartily fed up of losing semi-finals. 

Danny Cipriani in action for Gloucester against Bath in the Premiership

Seventh in the Premiership last year, Gloucester were the lowest placed side to sneak into this year's blue riband European event. 

However, they appear to be a more potent outfit with the arrival of the enfant terrible of English rugby, Danny Cipriani, who has made an excellent start to life at Kingsholm, earning the Premiership Player of the Month award for September. 

This, however, was not enough for him to earn a spot in Eddie Jones's England squad and didn't stop Luke Fitzgerald labelling him "a coward" this week. 

Johan Ackerman's team currently sit fourth in the Premiership after six games. 

Pool 3

Maro Itoje in action for Saracens in the Premiership

Saracens failed in their bid for three in a row European titles last year but regained their Premiership crown they look as imposing and primed as ever heading into the 2018-19 campaign. 

Mark McCall's team have an 100% record from their opening six Premiership games and they've registered heavy wins over Bath, Bristol and Gloucester already this season. 

Blast from the international past David Strettle, the first Englishman to score a try at Croke Park, signed from Clermont in the summer while Schalk Brits retired. Otherwise, the team has a familiar look. 

Their side contains some of England' most important players, notably: Owen Farrell, Maro Itoje and the Vunipola brothers. They are second-favourites overall behind Leinster and a massive threat. 

Finn Russell has departed and Stuart Hogg is injured but Glasgow have started the Pro 14 season well and currently sit where they finished last season - top of Conference A. 

Dave Rennie's side face a testing opening at home to Saracens in Scoutsoun. The coach has left a lot on the shoulders of young out-half Adam Hastings, son of Scottish rugby legend Gavin. 

Making their debut in the European Cup, Lyon were only promoted from the French second tier in 2016, finishing fifth in last year's Top 14 standings. 

Pierre Mignini's side have made a strong start to the present Top 14 season, with an away win over Racing 92 last weekend lifting them to third in the table. 

Experienced French out-half Jonathan Wisniewski will be depended upon to direct them through their debut Champions Cup season. Australian loose forward Liam Gill will also be influential. 

Challenge Cup holders Cardiff Blues boast plenty of talent in their ranks with Gareth Anscombe stationed at out-half. 

However, they are still coping with the premature retirement of Sam Warburton and the departure of Alex Cuthbert for Exeter. 

John Mulvihill's side have had a mixed start to the Pro 14 season but have won three on the bounce, including an emphatic win at home to Munster. 

Pool 4

Rhys Patchell scores against Ospreys at the weekend

Scarlets last year became the first Welsh side since Cardiff in 2009 to reach a European Cup semi-final but were blown away by a Leinster outfit hitting top gear in Lansdowne Road. 

Summer departures have presumably weakened them, with John Barclay, Tadhg Beirne and Scott Williams all gone elsewhere. 

Also, coach Wayne Pivac is soon to accede to the position of Wales head coach, just reward for his superb efforts with the region but hardly good news for the Scarlets themselves. 

Still, they have Rhys Patchell at fly-half, Pivac has another full season left in charge, and they have begun the Pro 14 season reasonably well. 

Simon Zebo has been in prolific try-scoring form early in his Top 14 career but last year's European runners-up Racing 92 have gotten off to an indifferent start in France.

The loss of Dan Carter and Yannick Nyanga may have weakened them but they've been spry in finding reinforcements, with Finn Russell joining from Glasgow Warriors. 

The Parisian side have a particularly strong pedigree in the competition with final appearances in 2016 and 2018. 

Simon Zebo is scoring freely since moving to Racing 92

Leicester Tigers have competed in every European Cup season that the English sides haven't boycotted, the only club to do so. 

They've rarely looked less intimidating than they do now. The 40-6 loss to Exeter Chiefs on the opening day of the season was enough of a jolt that the upper echelons decided to sack Matt O'Connor immediately. 

Under Geordan Murphy, they've won three and lost two in the Premiership table and remain in mid-table. The virtuoso out-half George Ford remains the leading man in the backs but they don't appear to have the fire-power to go deep in the competition this season. 

Ulster's win over Ospreys in May ensured that their traumatic 2017-18 season did at least end with Champions Cup qualification. 

Whether they'll be able to do anything in the tournament is doubtful.

There's been a big overhaul in personnel at the province with Jordi Murphy, Marty Moore and Billy Burns among the new arrivals replacing the departed Jared Payne, Andrew Trimble, Tommy Bowe, Paddy Jackson, Stuart Olding and Charles Piatau.

New coach Dan McFarland has had a rocky start to life in Ulster, including a record 64-17 Pro14 defeat to Munster.

A formative year for the province. 

Pool 5 

Vern Cotter's Montpellier team are top seeds in Pool 5

Vern Cotter lost his third Top 14 final as a coach in May when his table topping Montpellier side under-performed against Castres in the final. 

The club have only once escaped the pool phase, reaching the quarter-finals in 2013 when they lost to Cotter's Clermont team. 

Montpellier have an absurdly South African heavy side with ex-Ulster man Ruan Pienaar at scrum half, Bismarck du Plessis at hooker, Francois Steyn at centre and Jannie de Plessis at prop. 

As if that wasn't enough, they'd added full-back Johan Goosen over the summer, Racing's player of the year when they won the Top 14 in 2016. 

Bloodgate's own Dean Richards has proven his enduring coaching shrewdness by leading Newcastle Falcons from English rugby's second tier back to the Champions Cup in six years. 

Back in Europe's top competition for the first time since 2005, Newcastle have had nonetheless made a stuttering start to the present Premiership season.

Their 34-year old Fijian centre Vereniki Goneva was named Premiership Player of the Season last year and remains central to their hopes. Former England out-half Toby Flood re-discovered his form at the club. 

The 2011-12 semi-finalists Edinburgh return to Europe's premier tournament for the first time in three years thanks to a 3rd place finish in Conference B of the Pro 14 and a narrow loss to Munster in the quarter-final. 

Richard Cockerill's team are not fancied to progress beyond the pool phase, though they've added John Barclay and New Zealand out-half Simon Hickey to their ranks. 

They are currently running in fourth in Conference B of the Pro 14. 

Still frightening on paper, Toulon have made a poor start to the Top 14 season, losing four of their six matches, including heavy defeats to Stade Francais and Clermont Auvergne. 

The three-time European champions (2013-15) have drafted in New Zealanders Julian Savea and Liam Messam along with Welsh scrum half Rhys Webb. 

Follow Exeter v Munster on Saturday via our live blog on RTÉ.ie/sport and the News Now app or listen to exclusive national commentary on RTÉ Radio 1 at 3.15pm with commentary from Michael Corcoran and Donal Lenihan.

Follow Leinster v Wasps on Saturday (kick-off 7.45pm) via the live blog on RTÉ.ie/Sport and the News Now app.