With two decisive top-of-the-table encounters and a number of teams desperate to avoid having the threat of relegation from the World Rugby U20 Championship hanging over them, we're set for a day of drama on Wednesday as the pool stages reach a conclusion.

In Rosario, fans are in for a treat on what doubles as Keep Rugby Clean Day at the premier international age-grade tournament in Argentina.

Following on from Georgia's meeting with Scotland, defending champions France take on hosts Argentina to decide the winners of Pool A, before the action concludes with what should be a titanic tussle between two former champions in South Africa and New Zealand.

Some 180 kilometres away in Santa Fe, the triple bill begins with an all-Six Nations affair between Italy and Ireland, a match both sides need to win to avoid any chance of them finishing bottom of Pool B, while it is a similar situation for Wales and Fiji in Pool A in the second fixture of the day. England's Pool C match with confirmed semi-finalists Australia will bring the curtain down on proceedings there.

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POOL A: FRANCE v ARGENTINA

With a four-point lead over Argentina, a draw would be enough for France to confirm top spot in Pool A and keep their title defence alive. For Los Pumitas, nothing less than a win will do and even then that may not be enough if bonus points come into the equation.

Recent U20 Championship meetings have been closely-fought affairs with two wins apiece and no more than nine points separating the sides. Overall, France have won four matches at this level to Argentina's two.

Los Pumitas have been spared facing the tournament's top try scorer Jordan Joseph with Thibaut Hamonou wearing the number eight jersey instead in a pack showing two changes in total, the other seeing Loic Hocquet replacing Matthias Haddad on the blindside. Matthis Lebel and Julien Delbouis come into the starting line-up on the left wing and at inside-centre.

Argentina also make four changes, Geronimo Prisciantelli's introduction at inside-centre the only alteration to an otherwise settled backline. Meanwhile, props Thomas Gallo and Francisco Marchetti come into the front row and Juan Cruz Perez Rachel will pack down on the blindside.

POOL A: WALES v FIJI

While Fiji may have lost their first two games to sit bottom of Pool A, Wales coach Gareth Williams has seen enough in the Pacific Islanders' play to know that his side are in for a tough test on Wednesday.

“Fiji have played some excellent stuff this tournament, and have been a challenge early on for both France and Argentina. Therefore returning to the focus of the first two games is key for us," he said.

Williams has made four changes of personnel and one positional with Tiaan Thomas-Wheeler moving out one position to outside-centre. Captain Dewi Lake starts his third match at hooker but has two new props either side of him in Tom Devine and Nick George. Ed Scragg and Jac Price pack down behind them in an unchanged second-row, while the back-row triumvirate of Iestyn Rees, Tommy Reffell and Jac Morgan, so impressive in Saturday's 32-13 defeat to France, also remains intact.

The other changes come in the backs with Deon Smith tasked with filling the boots of Ryan Conbeer and Sam Costelow taking over from Max Llewellyn in midfield.

Fiji's starting line-up is unrecognisable from the one that went down to a 41-14 defeat at the hands of Argentina, coach Kele Leawere making 11 changes of personnel and two positional.

Inside-centre Taniela Soqonawasaloa is handed the captaincy for the first time, a couple of weeks short of his 20th birthday, and is joined in the midfield by Ilaisa Droasese, who moves from the right wing to outside-centre. Left-wing Epeli Momo is the only other back to retain his place.

Momo, Droasese and second-row Chris Minimbi are the only players to start every match for Fiji in this year's tournament. Vilive Miramira, who was a replacement in the first match against France, makes back-to-back starts but at openside not on the blindside.

In five previous U20 Championships meetings with Wales, Fiji have won just once – 34-20 in the fifth-place semi-final in 2011. 

POOL B: ITALY v IRELAND

Having missed out on a first-ever win over England by the slenderest of margins last time out, agonisingly losing 24-23, it will be fascinating to see how Italy respond for this pivotal match against an Ireland side that has had its fair share of injuries before and during the U20 Championship.

The Azzurrini have made six changes of personnel and one positional – Cristian Lai switching from the right wing to the left – as they bid to avoid becoming embroiled in a relegation battle, an all too familiar scenario for them at the U20 Championship.

Lorenzo Michelini comes in at loose-head to partner Niccolo Taddia and Matteo Nocera, the Azzurrini's trusted servants at hooker and tight-head, while the only other new face in the pack is Angelo Maurizi on the blindside. Davide Ruggeri continues to captain the side from openside. Alessandro Fusco and Paolo Garbisis are tasked with controlling the game at half-back, while Damiano Mazza and Jacopo Trulla come back into the side at inside-centre and on the right wing.

Already shorn of leading figures such as Harry Byrne before leaving for Argentina, Ireland have had to call for reinforcements to replace injured quartet Iwan Hughes, Sean French, John Hodnett and Stewart Moore. Ronan Watters, meanwhile, is following return to play protocols after a head injury sustained against Australia so is unavailable for selection.

With regular captain Charlie Ryan dropping to the bench, Six Nations Grand Slam winners Ireland will be led from outside-centre by Liam Turner – one of only five players to retain their place from the loss to Australia. Winger Angus Kernohan is the only other back to return, while in the forwards Josh Wycherley, Ryan Baird and David McCann line up at prop, second-row and blindside flanker. Cian Booth takes the place of Watters on the openside, fit-again Azur Allison is in for Hodnett at number eight and Cormac Foley replaces Moore in midfield.

“We are proud of the effort the players put in on Saturday against Australia given the circumstances, and the character they showed throughout the contest has to be commended. We have no doubt that they will dig deep again on Wednesday against the Italians,” said Ireland coach Noel McNamara, whose side would need to rack up the points against Italy to have a realistic chance of claiming the best runner-up spot in the semi-finals.

“Italy have been, and are a very good side and they showed that against England on Saturday. They have been consistently competitive at this tournament over the last number of years. The players are excited about the opportunity to get back out to play, and the focus is entirely on delivering a performance.”

POOL B: ENGLAND v AUSTRALIA

With Australia already through to the semi-finals and England unable to make it through to the last four for only the second time in U20 Championship history, it would easy to write this off as a dead-rubber. But given the historic rivalry between the nations and the fact England still need to win to be absolutely sure of their top-tier status next season, this encounter will be no less competitive than usual.

Oceania champions Australia name a side showing five changes as they look to finish the pool stages with a perfect record. Only once – in 2010, the year they reached the final – have the Junior Wallabies beaten England in six attempts at this level.

Nick Frost is rewarded for his two-try burst off the bench with a starting spot alongside Trevor Hosea in the second-row, while Joseph Cotton and Patrick Tafa come in at hooker and number eight respectively. The two changes to the backline see Henry Robertson and Joey Walton get the nod at scrum-half and outside-centre.

“We wanted to get a clean sweep in our pool stage,” Australia coach Jason Gilmore said. “We've said the whole way along that winning's a habit and we want to keep this momentum going into the semis. And it's another test match. It's a big one against England and the boys are really keen to play in this one.”

Failure to secure a bonus-point in Saturday’s victory against Italy resulted in England being eliminated from the title race earlier than ever before. Head coach Steve Bates has reacted by making five changes of personnel and three positional, one of them involving Josh Hodge whose heroics saved the day against Italy in round two.

Hodge's 73rd-minute penalty proved the difference against the Azzurrini and the Newcastle Falcons player keeps his place in the team – but on the left wing instead of at full-back. Fraser Dingwall moves out one position to outside-centre and Tom de Glanville reverts back to full-back having worn 10 last time out. Manu Vunipola and Cameron Redpath bring ball-playing nous to the team at fly-half and inside-centre respectively.

Upfront, Bates keeps faith with hooker Will Capon, second-row Richard Capstick and back-row duo, Aaron Hinkley and number eight Rus Tuima.

“This is a big fixture for us and the players know we need to raise the level and pace of our game against a good Australia side,” said Bates. “We always enjoy matches against southern hemisphere opposition, it’s not often these players get the opportunity to face the likes of Australia or New Zealand and they are very excited about that.

“The players feel like they haven’t played their best rugby yet in this competition and the challenge for them is to play with a bit more continuity in the game. We trained very well yesterday with that in mind and I’m hoping to see an exciting performance from us on Wednesday.”

POOL C: GEORGIA v SCOTLAND

Injury has deprived Scotland of centre Robbie McCallum, who scored a brilliant solo try against New Zealand in round two, with Grant Hughes named at 12 instead of him in a much-changed starting XV.

Murphy Walker, Ewan Ashman and Euan McLaren form a new-look front-row, Cameron Henderson joins Ewan Johnson in the second-row and Marshall Sykes, captain Connor Boyle and Tom Marshall are named as the back-row trio.

Roan Frostwick and Ross Thompson, who impressed off the bench in the 52-33 loss to New Zealand, are the starting half-backs while Cameron Anderson comes into the midfield with Rory McMichael shifting to the right wing to replace him. Jack Bain is rewarded for his try against New Zealand with another run out on the other flank and Matthew Davidson starts at full-back.

While pleased with aspects of his side's play so far, head coach Carl Hogg is looking for a step up in the level of performance, particularly in defence.

“I was proud of the players’ resilience to bounce back from a poor start against New Zealand,” Hogg said. “There were spells within the game where we were competitive and put them under real pressure, while I thought some of the tries we scored were an excellent example of the attacking blueprint we’re trying to implement. However, we must learn to be more robust and stop conceding soft tries if we are to convert these battling displays into results.

“Georgia, like South Africa and New Zealand before them, present a different challenge and we will have to adapt to their physical and forward-based style of play. We need to impose our own style of play on the contest while being respectful of Georgia’s strengths.”

Georgia full-back Dachi Papunashvili, at 17 years and 234 days the youngest player in the tournament, makes his first start in a radically overhauled Junior Lelos side. Only hooker Vano Karkadze, centre and new captain Demuri Tapladze and Otar Lashki survive from the starting XV that lost 48-20 to South Africa. Double try scorer Lashki switches from the left wing to the right for this encounter, one the Junior Lelos won 39-31 last year to record their best ever ranking of ninth.

POOL C: SOUTH AFRICA v NEW ZEALAND

A clash of the Titans brings the action at the Racecourse Ground in Rosario to a close as South Africa, a side that has medalled at every tournament bar one and lifted the trophy once, take on the six-time champions New Zealand in a match to decide who tops Pool C.

Despite New Zealand’s pedigree in the competition, South Africa have the superior head-to-head, winning the last five of their six encounters, including a 22-16 victory in the final before 35,000 people at Newlands in 2012. 

Continuity is the name of the game for South Africa as coach Chean Roux keeps changes to a minimum. Eligh Louw and Sibusiso Sangweni come into the pack in the second-row and back-row respectively, while in the backs Thaakir Abrahams is named on the wing. Influential blindside flanker Dylan Richardson, who capped a marvellous display against Georgia with a couple of tries, has overcome a knock in that game to take his place in the back-row alongside ever-present captain Phendulani Buthelezi.

“It is going to be a tough game. They (New Zealand) like to keep ball in hand and they have some exciting runners, so it will be the same as facing any typical New Zealand team, we need to be up for it and be ready for them,” said Roux.

New Zealand coach Craig Philpott has opted to freshen things up in selection, particularly in the pack where second-row Tupou Vaa'i is the only returnee. The three backs to survive from last weekend's 52-33 win over Scotland are fly-half Fergus Burke, who converted six of his side's eight tries, outside-centre Billy Proctor and winger Etene Nanai-Seturo, who switches from the left to the right flank.

“We have made a number of changes ahead of this match and there is a real sense of excitement in the group about going out and putting in a strong performance,” said Philpott.

“It doesn’t take much to motivate a group when they are pulling on the black jersey against South Africa, its important the team channel that energy and stick to our structures because we know it will be a hugely physical encounter.”