This weekend marks the return of rugby's premier club competition.

The result of one match has already been decided. Scarlets have been forced to forfeit Saturday's match against Bristol after their squad was caught in quarantine on their return from South Africa.

But for the rest, the road to Marseille starts here.

Who are favourites?

There is a strong French flavour at the front of the betting market.

Holders Toulouse, led by France's poster-boy half-back combination of Antoine Dupont and Romain Ntamack, are fancied to become the first side to retain the trophy since Saracens in 2016.

La Rochelle, the team they beat at Twickenham in last year's final, have brought in France international centre Jonathan Danty since finishing runners-up and now have former Ireland and British and Irish Lions fly-half Ronan O'Gara in the top coaching job.

Racing 92, three-time runners-up, have the sort of star-studded squad that can beat anyone on its day with Finn Russell and Virimi Vakatawa among the leading lights in an exciting backline.

While Bordeaux-Begles are the current pacesetters in the Top 14 with former Exeter wing Santiago Cordero among their running threats.

But the French won't have it all their own way.

Perennial Irish powerhouse Leinster, who won the most recent of their four titles in 2018, will surely be a feature of the latter stages. They provided 12 of the starting XV when Ireland beat the All Blacks last month.

The 2020 winners Exeter have made a patchy start to the season, but their quality runs deep. There may be an extra edge of hunger this year after seeing both their continental and domestic crowns slip away in 2021.

Leicester have put together a convincing case to be considered among the front-runners. Rejuvenated under the leadership of head coach Steve Borthwick, they are the runaway leaders in the Premiership with nine wins from nine.

Format

The pool stage was streamlined last season on "an exceptional basis" to minimise the Covid-19 risk and maximise the chances of getting games played.

With the pandemic still affecting everyday life, the 2020-21 format remains in place this season.

It's a complex one. These are the basics.

There are two 12-team pools. However not every team plays every other within those pools.

Instead, the teams are placed in one of four tiers based on their domestic league position last season.

If you came in the top two of the Premiership, Pro14 (as it was) or Top 14 last season, you are in tier one. If you came third or fourth, you are in tier two. And so on for the top eight in each league.

Each club's pool-stage fixture list is made up of four matches, home and away against two other teams.

Tier One clubs will play the two Tier Four clubs who are in their 12-team pool, but not if they are in the same domestic league.

Tier Two and Tier Three teams face off in a similar way.

Ones to watch

Paolo Garbisi - Montpellier

The 21-year-old fly-half is finally playing behind a pack that provide him with a platform after toiling in Italy and Benetton teams. He sparkles with ball in hand and has a canny kicking game.

Cameron Woki - Bordeaux-Begles

Part of a conveyor belt of young French talent, the 23-year-old was deployed in the second row for France's win over the All Blacks in the autumn but is more usually a flanker. A rangy, quick runner who provide a useful line-out jumping option.

Juarno Augustus - Northampton

A powerhouse number eight, who recently arrived at Franklin's Gardens from South Africa's Stormers. He was player of the tournament at the 2017 Under-20 World Championships and scored his first Northampton tries earlier this month with a brace in the win over Bath.

Alfie Barbeary - Wasps

Another fine back row prospect, Barbeary was on the brink of an England debut last year before injury intervened. Deft hands, fleet feet and bundles of power and aggression make the 21-year-old a handful for any defence.

What they say

La Rochelle head coach Ronan O'Gara:

"The French domestic game is strong now, the French international game is very strong. It is an appealing place to a lot of people.

"There is massive excitement for the Rugby World Cup here in 2023. Rugby is getting very, very popular and the standard of club rugby seems to be getting better and better, it makes for an unbelievably exciting European Cup."

Leinster fly-half Johnny Sexton:

"We feel in the losses to Saracens and La Rochelle in the past two seasons, we feel that we didn't put our best performances out there.

"When you look back with regrets it hurts the most, but we know we are not far away and we need to work hard to make sure we are in the best position possible to be ready when those big days come at the end of the season."

Clermont Auvergne head coach Jono Gibbes:

"You realise how incredibly difficult it is to win this tournament because it is the elite.

"The love affair between Clermont and the European Cup is still very, very strong. They have been hurt and had their heart broken, but it is still a big part of the ambition of this town. When the European weeks come around the whole place has a lift and a different energy about it."

Glasgow captain Fraser Brown:

"This is an opportunity to play the best teams in Europe and show the sort of rugby we want to play and the quality we have up here.

"At both Glasgow and Edinburgh there is a lot more quality throughout the squad and the guys coming back from playing for Scotland have to fight for their position.

"There are real selection dilemmas and that speaks to the improvement in quality across the whole game in Scotland."