Rugby fans from around the world await four blockbuster tests this weekend. Games can offer compelling evidence that the once-yawning chasm between Northern and Southern Hemisphere rugby is now little more than a crack, with the World Cup just 14 months away.

In Wellington, Sydney, Cape Town and Santiago del Estero on Saturday, eight of the world's best teams play deciding matches in north-south series to conclude the first proper mid-year test window since the COVID-19 pandemic. An unprecedented northern sweep of last weekend's second tests saw Ireland stun the All Blacks, Wales upset the Springboks, England strike back against the Wallabies and Scotland level up their series against Argentina.

Southern Hemisphere powers New Zealand, South Africa and Australia have won eight of the nine World Cups between them but all are just 80 minutes away from embarrassment on home soil.

The world rankings already reflect a regional shift, with France and Ireland keeping the southern nations out of the top two for the first time since the listing was introduced. Ireland could go top with a win at Wellington Stadium, where they will be looking to hand New Zealand straight home losses for the first time in 24 years. The All Blacks backlash is a phenomenon well known to teams who have had the temerity to beat New Zealand, but Ireland coach Andy Farrell said his players had no qualms about facing it. "We want this, I have to emphasise that," he said in the New Zealand capital on Thursday. "To have them in the last game before we break for the season, for them to be fired up, wanting to prove a point to them and to us, it really does not get any better."

Riding high after a historic first win over the All Blacks in New Zealand, Ireland are ready to unleash "chaos" in Wellington to upset the hosts again and claim a seismic series victory.

Spanked in the Eden Park opener, Andy Farrell's men rebounded magnificently against the shorthanded hosts in Dunedin to set up a mouth-watering third test decider that brings the tension of a World Cup knockout a year early for fans. Tenacious Ireland have relished their role as New Zealand disruptors, winning four of the last seven matches they have played against the three-time world champions. They will need to lift again at Wellington Regional Stadium, where a chastened All Blacks team are likely to come out breathing fire.

Home fans will hope that means more discipline from the All Blacks, who drew two yellow cards and had prop Angus Ta'avao dismissed in little more than half an hour at Dunedin.

Fans and media pundits have raged over the officiating in the series, criticizing the strict application of high contact rules and the regular disruptions brought by the referees consulting with TV match officials. English referee Wayne Barnes will control the match in Wellington.

Wales secured their maiden win over the Springboks in South Africa last weekend and have history in their grasp against the world champions at Newlands on Saturday. "It's going to be a fair old challenge for us, we know that," said coach Wayne Pivac. "But I think all the soreness, and the tiredness of the tour goes out of the window when you get that adrenaline, and kickoff comes."

Scotland face a different challenge in their decider in the Argentine interior, tasked with reasserting northern dominance over a slowly growing southern power in the Pumas. Neither has it anymore going into the last and decisive rugby match of their first three-test series, not after both tore up their own lineups.

The Pumas and Scotland pressed the reset button ahead of their series ‘final’ in the provincial city of Santiago del Estero by making unusual wholesale changes. Scotland announced eight changes and Argentina 12, including one positional shift.

A high number of changes usually indicates rotation of a squad, but Argentina is highly motivated to snatch a first home series in 15 years and Scotland insists the primary aim of the tour is to win the series ahead of player development. Which makes all the team chopping and changing appear excessive and counter to forming cohesion.

The first test in Jujuy was won well by Argentina 26-18 when a big lead was blown but recovered in style. Knowing Scotland would rally in the second test in Salta last weekend, Argentina's promise of improvement never materialized. Argentina was second best in scrums and rucks, slow again out of the gate after halftime, and a waster of chances. Four tries went begging in the second half.

New coach Michael Cheika reacted this week with what he called "a nice mix of opportunity and continuity." He kept only lock Guido Petti in the pack, flyhalf Santiago Carreras, center Matias Orlando in his 50th test, and Emiliano Boffelli, who was switched back to the wing from fullback.

Injuries ruled out picking captain and hooker Julian Montoya, wing Santiago Cordero, flyhalf Benjamin Urdapilleta and backup halves Felipe Ezcurra and Domingo Miotti. Montoya misses his first test since the 2018 Rugby Championship after 33 straight appearances.

The captaincy has gone to recovered No. 8 Pablo Matera after it was stripped from him at the end of 2020 for historical tweets, and the No. 2 jersey to former skipper Agustin Creevy for his first start since the 2019 Rugby World Cup.

Into the pack comes Tomas Lavanini, who received a world record third red card in his last test, against Ireland in November.

Lautaro Bazan Velez will debut as Argentina's fourth scrumhalf of the series. Bazan Velez recently finished more than five years with Argentina sevens following a Tokyo Olympics bronze medal. "He's not played much 15s," Cheika said, "but he's got speed and got an engine." Two more could make debuts off the bench; hooker Ignacio Ruiz, and flyhalf Tomas Albornoz, fresh from Argentina XV wins over Georgia and Portugal.

Another feature of the backline is Juan Cruz Mallia restored at fullback where he impressed in Jujuy. "We need to believe in ourselves, change some habits, improve those habits, and that takes time," Cheika said. "This next game is about how we get up and fight again." Following Scotland's best half of rugby in 18 months, coach Gregor Townsend's response to winning 29-6 was to change half the pack which dominated Argentina, and drop scrumhalf Ben White, who was the backline star in Salta.

With lock Grant Gilchrist left out, the captaincy has passed to flanker Hamish Watson, who played his 50th test last weekend and missed a tackle for the first time since his 25th.

Injuries to backs Darcy Graham, Rory Hutchinson and Kyle Rowe have given uncapped Glasgow fullback Ollie Smith a test debut while Blair Kinghorn, the Edinburgh fullback whom Townsend is trying to convert into a test flyhalf, was retained. "Opportunity is the word to describe this tour," Townsend said. "I know they have got one big performance left."

That the England-Australia is going down to the final match is less surprising given Eddie Jones's team won 3-0 on their last tour Down Under before going on an eight-match winning streak against the Wallabies.

Wallabies captain Michael Hooper believes the gap between the leading rugby nations is now paper-thin. "It's definitely been the story over the last few years, there are no easy games," he said on Friday at the Sydney Cricket Ground. "Every game, it is super competitive, it's going down to the wire. I think it's great for rugby, great for the fans. I know in our series, it's been two great tussles and I expect tomorrow to be no different." The Sydney Cricket Ground has witnessed dozens of contests between Australia and England over the years but few with the level of brutality anticipated in Saturday's rugby test between the Wallabies and Eddie Jones's tourists. The series is tied at 1-1 after two engrossing tests and the hallowed cricket venue gets to plays host to a mouthwatering decider while the finishing touches are added to the Sydney Football Stadium being rebuilt next door.

Australia won the opening test 30-28 in Perth but were blown off the park in the first half an hour of the second test in Brisbane, the ensuing 25-17 loss compounded by a lengthy injury list. That early England onslaught at Lang Park means the Wallabies know they must respond, and respond early, to England's physicality or risk losing a 10th test in their last 11 encounters with Jones's team. Australia coach Dave Rennie was forced into a raft of changes by injury and suspension with the result that blindside flanker Harry Wilson will play his first test of the year. "It's been a pretty brutal series so far, as injuries on both sides will tell us, but Harry's fresh and keen to rip in," coach Dave Rennie said on Thursday. "We were disappointed with last week, we are better than that. We need to be more clinical, we need to be better. There's no doubting the character of this group, and we'll fight."