Pool A
Ireland (world ranked 1)
Key man - Conor Murray
His tactical kicking is crucial to Ireland’s gameplan. The opposition termed him the world’s best scrum-half when he toured New Zealand with the British & Lions two years ago.
One to watch – Jordan Larmour
Just 22, the speedy wing has already earned a reputation for being the scorer of eye-catching tries
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Scotland (7)
Key man – Hamish Watson
In a Scotland side that has plenty of flair, Watson provides industry and a hard edge from the back row.
One to watch – Finn Russell
Talking of flair, few have more of it than Scotland’s lead entertainer. Unpredictable, which can be a mixed blessing, but always good to watch
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Japan (10)
Key man – Michael Leitch
The talisman of that extraordinary win over South Africa in Brighton four years ago, the flanker remains the leading figure in Japanese rugby.
One to watch – Fumiaki Tanaka
Once deemed by Eddie Jones to be the funniest man in rugby, the impish scrum-half is back for his third World Cup.
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Russia (20)
Key man - Vasily Artemyev
Russia’s captain and full-back went to school in Ireland, played for Irish Universities – but is now closing in on 100 caps for his country.
One to watch - Tagir Gadzhiev
From Dagestan, like UFC superstar Khabib Nurmagomedov, and he was a mixed martial artists and kickboxer, too, before taking up rugby.
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Samoa (16)
Key man – Chris Vui
Came to rugby in his late teens, and was an apprentice carpenter when he was offered his first pro deal. Became Samoa captain within a year of his Test debut.
One to watch – Tim Nanai-Williams
Once hoped to play for New Zealand, where he was born and excelled in Super Rugby, before switching allegiance to Samoa in time to play at the World Cup in 2015.
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Pool B
New Zealand (2)
Key man – Beauden Barrett
One of five brothers, three of whom are in this World Cup squad. Barrett might be the world’s best fly-half – but could play much of this tournament at full-back.
One to watch – Richie Mo'unga
His form in guiding Crusaders to a 10th Super Rugby title, as well as injury to Damian McKenzie, prompted the reshuffle that sent Barrett to full-back and Mo’unga to No 10.
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South Africa (4)
Key man – Faf de Klerk
Impossible to miss, given his flowing blond locks and his omnipresence on the field. The scrum-half is the Boks’ heartbeat.
One to watch – Cheslin Kolbe
Dubai rugby followers knew all about Kolbe’s quick-stepping skills before the wider world. He played at The Sevens, long before becoming the global star he is today.
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Italy (14)
Key man – Sergio Parisse
His powers might be on the wane, but the No 8, who turned 36 last week, remains Italy’s leader.
One to watch - Matteo Minozzi
Finding his way back after injury, the wing will be Italy’s best attacking threat. He has seven tries in 13 Tests so far.
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Namibia (23)
Key man - Johan Deysel
Namibia’s captain enjoyed perhaps the finest moment in his country’s rugby history when he touched down a try against New Zealand in the 2015 World Cup.
One to watch – Janco Venter
Jacques Burger may be retired now, but Namibia still have some back-row strength in the form of Venter.
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Canada (22)
Key man – DTH van der Merwe
The wing is heading to his fourth World Cup with Canada, and will be hoping to add to his try haul of six in that time.
One to watch – Phil Mack
Now 34, the scrum-half is back for a second World Cup appearance, two years after retiring from a fine career in sevens.
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Pool C
England (3)
Key man – Owen Farrell
Seventy-six caps, and still only 27. England’s team will be built around Farrell – no matter whether he plays No 10 or 12.
One to watch – Manu Tuilagi
Optimism abounds that one of England’s finest talents might be able to leave injury and off-field difficulties aside for a proper tilt at a World Cup.
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France (8)
Key man – Antoine Dupont
Still only 22, but the scrum-half is regarded as the shining light to lead France away from their years of gloom.
One to watch – Alivereti Raka
A product of Clermont’s Fiji-based academy, the wing scored a try on Test debut against Scotland in August.
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Argentina (11)
Key man – Agustin Creevy
No longer the captain, nor guaranteed to play every minute, but his legend status is long since established among Argentina’s rugby fraternity.
One to watch – Pablo Matera
The flanker, who inherited the Pumas captaincy from Creevy last year, was a key figure in the Jaguares side who reached the Super Rugby final for the first time this season.
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United States (13)
Key man - Joe Taufete'e
The American Samoa-born Californian is remarkably prolific for a hooker. In 22 Tests to date – seven as a replacement - he has scored 20 tries.
One to watch – Martin Iosefo
The wing, who learnt rugby while growing up in Hawaii, scored 16 tries as USA came within an ace of winning the World Sevens Series last season.
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Tonga (15)
Key man – Siale Piutau
Tonga’s captain plays in England for Bristol alongside his younger brother, the celebrated former All Blacks wing Charles Piutau.
One to watch - Ben Tameifuna
The France-based prop is said to be the heaviest player in world rugby, having weighed in at 153kgs ahead of a Test match last year.
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Pool D
Australia (6)
Key man – David Pocock
Made his return to playing in Australia’s final warm up match after seven months out with injury. This will be his last tournament for the Wallabies.
One to watch – James O'Connor
The controversial back was only restored to Australia’s set up in July after a six-year absence from Test rugby.
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Wales (5)
Key man – Dan Biggar
Some Welsh legends claim they will not win the World Cup with Biggar at fly-half. Well, they are going to have to try, given Gareth Anscombe is out injured.
One to watch – Josh Navidi
The dreadlocked back-rower, who is also a surfer, has just the sort of strength you might expect from the son of a wrestler.
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Georgia (12)
Key man – Mamuka Gorgodza
One of the outstanding players of the last World Cup, and surely Georgia’s greatest ever, he is returning to Test rugby after a two-year absence.
One to watch – Vasil Lobzhanidze
The scrum-half became the youngest World Cup player when he played in 2015 aged 18 years and 340 days. Four years on, he has nearly 50 caps.
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Fiji (9)
Key man – Leone Nakarawa
Better offloading skills than Sonny Bill Williams. And yet he plays in the second row. Which is the sort of thing that could only happen in Fiji.
One to watch – Josua Tuisova
Part of the gold-medal winning side at the Rio Olympics in 2016. So muscle-bound, he can rarely find socks that fit over his calves
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Uruguay (19)
Key man – Diego Magno
Uruguay’s most-capped player turned 30 earlier this year. The flanker is closing in on 100 appearances.
One to watch – Santiago Arata
Thirteen tries in 39 matches for Uruguay’s senior team is an impressive return from a scrum-half who turned 23 earlier this month.