Paris - Already the kings of Europe for the last two years and top of the English Premiership, Saracens will be boosted by the return of British and Irish Lions flyhalf Owen Farrell for the start of their European Champions Cup defence.
Ulster and Wasps get this season's competition underway on Friday night before the champions make their bow on Sunday away to domestic rivals Northampton.
The two sides met on the opening day of the Premiership season with Sarries running in nine tries in a 55-24 thrashing at Twickenham, and that without Farrell.
As well as the half-back, South African forwards Schalk Burger and Schalk Brits could also return from injuries.
"Owen has trained for two days and is fine. Schalk Burger and Schalk Brits have a chance of being available," Saracens' director of rugby Mark McCall said.
"For Brits it will be soon after having his appendix out, so that would be a decent turnaround. He trained (on Wednesday) and if he has no reaction he has a great chance of being involved."
Saracens not only defended their title last season but also set a new record of 18 European matches in a row unbeaten as they defeated Clermont, the French champions, 28-17 in the Edinburgh final.
The north Londoners already look to have hit their stride this season, despite the absence of key players such as Farrell and England No 8 Billy Vunipola, out until the new year with a knee injury.
Getting off to a good start will be vital in a pool that includes Clermont - beaten finalists in three of the last five years - and Ospreys.
With such fierce opposition, it could be one of the groups whose runners-up fail to make the knock-out stages.
Clermont begin their campaign in Wales looking to end a run of four straight defeats on their travels this season.
And they are unlikely to be able to welcome back France centre Wesley Fofana for the trip to Swansea.
But coach Franck Azema was feeling positive despite Sunday's 28-18 defeat at Toulouse.
"I think we're on the right track. It will do us good to start the European Cup with an away match and knowing that every point counts," he said.
Both Sarries and Clermont played on Sunday, as did Wasps - thumped 38-19 by the European champions - who start their campaign on Friday night with a tough trip to Belfast.
It means they have a five-day turnaround, something McCall described as "grossly unfair".
On top of that, Wasps are missing 15 players through injury, including flyhalf Danny Cipriani and No 8 Nathan Hughes.
"It's not ideal by any stretch of the imagination," Wasps' director of rugby Dai Young told BBC Radio 5 live.
"There is very little we can do about it. We've known for a number of weeks what was the case, and we've just got to get on with it."
Wasps have had a poor start to the season, losing four matches in a row but their pool does appear one of the less tricky ones, with French debutants La Rochelle and Harlequins, who have been an English mid-table side for last few seasons.
And this is still the side that topped the regular Premiership standings last season, before losing to Exeter in the final.
English champions Exeter have not excelled in Europe so far but will be expecting to finally make their mark, albeit in what appears a tough pool alongside Leinster, Glasgow and Montpellier.
Three-time champions Toulon look to have drawn the long straw in a pool alongside Bath, Scarlets and Italians Treviso.
It may be the last time an Italian team is seen in the Champions Cup for some time with qualification rules changing for next season, based solely on final league positions and not on nationality.
Since the Champions Cup was reduced from 24 to 20 teams, no Italian side has qualified through merit.