Ahead of Sunday's four Heineken Champions Cup clashes, which include the start of Exeter's title defence, we take a look at each club's form, team news and key players...
Lyon vs Gloucester Rugby, 1pm
Form: When the 2019/20 Top 14 season was cancelled, Lyon were sat second in the table. The 2020/21 Top 14 season began back in September, and from nine fixtures so far, Lyon have won six, drawn one and lost two to sit fifth in the standings.
Having begun the season with two losses (Racing 92 at home, Toulon away), they have responded superbly and picked up some eye-catching wins: Bordeaux Begles at home, Bayonne at home, Toulouse away, Agen away, Stade Francais at home, and most recently league leaders La Rochelle at home.
Gloucester have struggled, however, with two heavy defeats from three Premiership games in the 2020/21 campaign. They began with a 38-15 loss at last season's strugglers Leicester Tigers, before beating Wasps at home but losing to 14-man Harlequins 34-24 at home last time out.
Key players: Lyon may be a name largely unheralded in Europe, but they contain some extremely talented players within their squad. Within the forwards, former Worcester hooker Joe Taufete'e, France prop Demba Bamba, Argentina prop Francisco Gómez Kodela, France lock Kilian Geraci and Wallabies second row Izack Rodda stand out.
Lyon also possess France's Mathieu Bastareud - who is being used as a No 8 - wing Noa Nakaitaci and outstanding Fiji wing Josua Tuisova.
With key men and leaders Jake Polledri, Ben Morgan and Billy Twelvetrees all out injured, and the experience and quality of wing Jonny May, scrum-half Joe Simpson and playmaker Danny Cipriani all left out, a lot will rest on the shoulders of flanker and skipper Lewis Ludlow.
Team News
Lyon: 15 Toby Arnold, 14 Xavier Mignot, 13 Pierre-Louis Barassi, 12 Charlie Ngatai, 11 Noa Nakaitaci, 10 Jonathan Wisniewski, 9 Baptiste Couilloud (c); 1 Xavier Chiocci, 2 Mickael Ivaldi, 3 Clément Ric, 4 Felix Lambey, 5 Izack Jon Rodda, 6 Loann Goujon, 7 Dylan Cretin, 8 Mathieu Bastareaud.
Replacements: 16 Jeremie Maurouard, 17 Raphael Chaume, 18 Vivien Devisme, 19 Killian Geraci, 20 Colby Fainga'a, 21 Jean-Marc Doussain, 22 Leo Berdeu, 23 Thibaut Regard.
Gloucester Rugby: 15 Kyle Moyle, 14 Jacob Morris, 13 Henry Trinder, 12 Tom Seabrook, 11 Alex Morgan, 10 George Barton, 9 Steve Varney; 1 Jamal Ford-Robinson, 2 James Hanson, 3 Ciaran Knight, 4 Ollie Atkins, 5 Jamie Gibson, 6 Jack Clement, 7 Lewis Ludlow (c), 8 Seb Nagle-Taylor.
Replacements: 16 Todd Gleave, 17 Alex Seville, 18 Jay Tyack, 19 Alex Craig, 20 Josh Gray, 21 Freddie Thomas, 22 Charlie Chapman, 23 Charlie Sharples.
Exeter Chiefs vs Glasgow Warriors, 3.15pm
Form: Defending European Cup champions Exeter are flying in the Premiership having coasted to three wins from three so far. Each win has been utterly comprehensive as well: Harlequins away (33-3), Bath at home (40-3), Leicester Tigers away (35-13). Having boasted three bonus-point wins too, they sit top of the Premiership by three points.
Glasgow on the other hand, are on a dreadful run of form. From eight PRO14 games so far this season, Glasgow have lost six: Connacht away, Ospreys away, Leinster at home, Ulster away, Munster at home and even the Dragons at home most recently. The Warriors haven't won since beating Scarlets on October 11. They are really up against it heading to Sandy Park.
Key players: Skipper, place-kicker and playmaker, Exeter out-half Joe Simmonds continues to be the Chiefs' key man. Ignored by Eddie Jones and England despite leading his club to an unprecedented domestic and European double last season, the 23-year-old has remarkable experience for a player so young. He marshals a hardy Chiefs forward back and talented back-line brilliantly.
Without their internationals, Glasgow have really struggled. They've also lost some of their most important players in recent seasons - including Finn Russell to Racing 92, as well as full-back Stuart Hogg and second row Jonny Gray to Sunday's opponents. As such, scrum-half Ali Price has become vital and rejoins the squad after a positive Autumn Nations Cup showing for Scotland.
Team News
Exeter Chiefs: 15 Stuart Hogg, 14 Olly Woodburn, 13 Henry Slade, 12 Ollie Devoto, 11 Tom O'Flaherty, 10 Joe Simmonds, 9 Jack Maunder; 1 Alec Hepburn, 2 Jack Yeandle (c), 3 Harry Williams, 4 Jonny Gray, 5 Sam Skinner, 6 Dave Ewers, 7 Jannes Kirsten, 8 Sam Simmonds.
Replacements: 16 Luke Cowan-Dickie, 17 Ben Moon, 18 Marcus Street, 19 Jonny Hill, 20 Richard Capstick, 21 Sam Hidalgo-Clyne, 22 Harvey Skinner, 23 Ian Whitten.
Glasgow Warriors: 15 Glenn Bryce, 14 Tommy Seymour, 13 Nick Grigg, 12 Sam Johnson, 11 Lee Jones, 10 Peter Horne, 9 Ali Price; 1 Oli Kebble, 2 George Turner, 3 Zander Fagerson, 4 Rob Harley, 5 Scott Cummings, 6 Ryan Wilson (c), 7 Tom Gordon, 8 Matt Fagerson.
Replacements: 16 Grant Stewart, 17 Aki Seiuli, 18 Enrique Pieretto, 19 Kiran McDonald, 20 TJ Ioane, 21 Sean Kennedy, 22 Brandon Thomson, 23 Huw Jones.
Racing 92 vs Connacht Rugby, 3.15pm
Form: Beaten Champions Cup finalists to Exeter in October, Racing have won seven and lost three games from 10 fixtures since the return of Top 14 action in September, to sit third in the table behind Toulouse and La Rochelle - though with a game in hand.
Wins have come against Lyon away, Montpellier at home, Stade Francais away, Pau at home, Brive away, Bayonne at home and most recently away at Bordeaux Begles. Defeats have come at home to Toulouse, and away at Castres and La Rochelle.
Connacht face a tough ask travelling to La Defense Arena first up, though their PRO14 form has been positive, with a couple of blips. The Irish province have registered four wins and two defeats from six league games, beating Glasgow at home, Edinburgh away, Zebre away and Benetton at home. Defeats have come away at Cardiff Blues and at home to the Scarlets.
Key players: Among a catalogue of potent backs, out-half Finn Russell is the man that makes Racing 92 tick. Centre Virimi Vakatawa is one of the most talented players in the world, but Russell's importance to Racing is enormous. He wins them most games, but can lose them encounters too such is his style of play.
For Connacht, their key player without a shadow of a doubt is centre Bundee Aki. Immensely powerful, hugely vocal and a player who never, ever gives up in Connacht or Ireland green. His selection to begin Sunday from the bench must be to provide substantial impact.
Team News
Racing 92: 15 Kurtley Beale, 14 Teddy Thomas, 13 Virimi Vakatawa, 12 Henry Chavancy (c), 11 Donovan Taofifenua, 10 Finn Russell, 9 Teddy Iribaren; 1 Eddy Ben Arous, 2 Camille Chat, 3 Georges Henri Colombe, 4 Bernard Le Roux, 5 Dominic Bird, 6 Wenceslas Lauret, 7 Baptiste Chouzenoux, 8 Fabien Sanconnie.
Replacements: 16 Kevin Le Guen, 17 Guram Gogichashvili, 18 Cedate Gomes Sa, 19 Donnacha Ryan, 20 Ibrahim Diallo, 21 Maxime Machenaud, 22 Antoine Gibert, 23 Simon Zebo.
Connacht: 15 John Porch, 14 Alex Wootton, 13 Sam Arnold, 12 Tom Daly, 11 Matt Healy, 10 Jack Carty, 9 Kieran Marmion; 1 Denis Buckley, 2 David Heffernan, 3 Finlay Bealham, 4 Eoghan Masterson, 5 Ultan Dillane, 6 Sean Masterson, 7 Jarrad Butler (c), 8 Paul Boyle.
Replacements: 16 Shane Delahunt, 17 Jordan Duggan, 18 Jack Aungier, 19 Cian Prendergast, 20 Conor Oliver, 21 Caolin Blade, 22 Bundee Aki, 23 Tiernan O'Halloran.
Munster vs Harlequins, 5.30pm
Form: Munster's form heading into the Champions Cup couldn't be better. Indeed, they have picked up seven victories from seven in the PRO14 - a run of results which include wins over full-strength Scarlets (away) and Edinburgh sides ahead of the Test window, plus over the Cardiff Blues and away at Glasgow Warriors.
It is the Irish province's best start to a season since 2001, with them sat top of Conference A.
Quins are in good form so far this season too, with two strong wins from three. They began the new Premiership campaign with a highly disappointing 33-3 loss to defending champions Exeter at the Stoop - a game which was still 12-3 with 10 minutes left - before responding with back-to-back away wins over Northampton (49-29) and Gloucester (34-24).
Key players: Munster welcome back nine players from Ireland camp ahead of this one, including the likes of Peter O'Mahony, Conor Murray, CJ Stander and Keith Earls, but perhaps their key man so far this season has been World Cup-winning Springbok centre Damian de Allende.
The 29-year-old has proven an exceptional signing so far, and with compatriot Andre Esterhuizen missing for Quins, De Allende will hope to grab his European debut by the scruff.
Marcus Smith was particularly impressive last time out at 10 for Quins, but their key man continues to be No 8 Alex Dombrandt. From three games so far, the 23-year-old has scored three games, with dynamism, carrying and try-scoring ability crucial for Paul Gustard and co. He captains the side on Sunday too.
Team News: For Munster, the headline news is the selection of in-form Gavin Coombes for his European debut within a back-row alongside O'Mahony and Stander. Like most recently for Ireland, O'Mahony shifts from the blindside to openside. Elsewhere, experienced half-backs Murray and JJ Hanrahan have held off the challenges of talented youngsters Craig Casey and Ben Healy.
For Quins, Springbok centre Esterhuizen is suspended and will have to wait for his European Cup debut, having been red-carded for elbowing Gloucester's Lloyd Evans in the face. Prop Simon Kerrod is also suspended for his part in the Barbarians' October excursion. Joe Marchant and Chris Ashton are listed as unavailable for selection.
Munster: 15 Mike Haley, 14 Andrew Conway, 13 Chris Farrell, 12 Damian de Allende, 11 Keith Earls, 10 JJ Hanrahan, 9 Conor Murray; 1 James Cronin, 2 Kevin O'Byrne, 3 Stephen Archer, 4 Jean Kleyn, 5 Tadhg Beirne, 6 Gavin Coombes, 7 Peter O'Mahony (C), 8 CJ Stander.
Replacements: 16 Rhys Marshall, 17 Josh Wycherley, 18 John Ryan, 19 Fineen Wycherley, 20 Jack O'Donoghue, 21 Craig Casey, 22 Ben Healy, 23 Rory Scannell.
Harlequins: 15 Mike Brown, 14 Nathan Earle, 13 Luke Northmore, 12 Ben Tapuai, 11 Cadan Murley, 10 Marcus Smith, 9 Danny Care; 1 Joe Marler, 2 Scott Baldwin, 3 Wilco Louw, 4 Hugh Tizard, 5 Glen Young, 6 James Chisholm, 7 Will Evans 8 Alex Dombrandt (c)
Replacements: 16 Elia Elia, 17 Santiago Garcia Botta, 18 Fin Baxter, 19 Richard De Carpentier, 20 Tom Lawday, 21 Scott Steele, 22 James Lang, 23 Ross Chisholm.