Calculators at the ready, it’s the final round of the RBS 6 Nations 2015 and as many as four teams are still in with a shout of lifting the trophy.

So competitive has this Six Nations been that for the first time in the history of the championship the lead has changed hands after every single round.

As things stand, England head the group of three teams on six points going into ‘Super Saturday’ due to a marginally better points difference (+37) than second-placed Ireland (+33) with Wales on +12. France have an outsider’s chance of claiming the silverware having won a game fewer than their rivals to sit on four points.

And there has been much to-ing and fro-ing in the World Rugby Rankings too, in this most intriguing of Six Nations, particularly in the battle for third spot and the right to be called the northern hemisphere’s leading team.

Ireland currently hold sway on 85.32 points, but with only 0.21 of a rating point advantage over England the situation could quite easily change again after what promises to be the most thrilling of conclusions to the Six Nations.

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While an Ireland victory over Scotland by more than 15 points could have serious implications on the destiny of the title given they’d have a double-figure points difference advantage over England, it would have little material effect on their ranking. Scotland’s current ranking of 10th means such a victory would be rewarded with less than half a ranking point, which is not enough to trouble the top two nations, New Zealand and South Africa.

But should Ireland lose at Murrayfield, as they did on their last visit in 2013, and England edge France at Twickenham, then Stuart Lancaster’s men would not only dethrone the defending Six Nations champions and claim only their second title since 2003 – depending on Wales’s result in Italy – they’d also recapture third spot in the rankings. A win for Scotland over Ireland would be rewarded with a one-place rise for Vern Cotter's men to ninth.

Wales need a big win in the opening game on Saturday if they are to crank up the pressure on Ireland and England. They have won their last seven encounters with Italy since slipping up at the Stadio Flaminio in 2007, and are bidding for their third title in four years.

The prize of third place in the rankings is also within the Dragons’ grasp if they win and there are surprise defeats for both Ireland and England. Depending on the margin, it is possible for Ireland and Rugby World Cup 2015 hosts England to lose even more points and fall as low as fifth and seventh in the rankings respectively. England’s lowest position since the rankings began in 2003 is eighth.

Italy can slip from their lowest ever position of 14th if they lose and Georgia  win in the European Nations Cup, but on the other hand 10th place could be theirs if they turn the tables on Wales with an emphatic victory and Scotland also lose by more than 15 points at Murrayfield. 

Defeats for Wales and Ireland in the first two fixtures of the day would open the door for France, who’d head to Twickenham to play England knowing that a winning margin of more than eight points would see them pull off the most unlikely of titles. If successful by twice that margin, they would leapfrog England and Wales in the rankings and move up to fifth.

Top two to face off

The Six Nations is not the only competition this weekend that could result in positional changes to the World Rugby Rankings as the first stage of the European Nations Cup 2016 Division 1A is coming to a climax with RWC 2015 bound Georgia and Romania occupying the top two positions in the table ahead of their meeting this weekend in Bucharest.

Georgia could climb as high as 14th if they win a 10th successive European Nations Cup match and Italy lose in Rome, while also condemn Romania to fall below Canada. However a first win over the Lelos since 2010 would promote Romania up the rankings and above USA to 16th. 

Any form of win for Portugal against Russia would result in a one-place rise for the side currently ranked 23rd in the world. Portugal have won on Russian soil on three previous occasions, in 2003, 2005 and 2011. Russia could fall two places to 21st depending on the margin of their defeat and a Spanish victory in Madrid.

Germany, still searching for a first win since returning to the top tier of the European Nations Cup this season, could climb as many of four places to 24th if they open their account with a resounding win against Spain. It was a close run thing the last two the two nations met in 2010, Spain prevailing by 21-17 in Heidelberg. Spain have won six games to Germany’s three since the sides first clashed in 1929. 

Raising the Bar-bados

The NACRA (North America Caribbean Rugby Association)Championship  continues this weekend with the outcome of two matches – Barbados (73rd) against Trinidad and Tobago (52nd) and Bahamas (86th) against Bermuda (62nd) – potentially impacting on the rankings. Good wins for the higher ranked away teams would result in a climb of two places up the rankings.

Barbados could gain five places if they manage to turn the formbook upside down and beat Trinidad and Tobago for only the second time in nine attempts, while the Bahamas, who have a won one, lost five head-to-head record against Bermuda, can move up three places shoud they come out on top.

Bermuda began their North Zone League Cup fixtures a fortnight ago,  posting a half-century of points on the Turks and Caicos Islands, while Barbados were on the wrong side of a 48-22 scoreline against defending champions Guyana in the South Zone Championship.

This weekend's other NACRA Championship matches between Cayman Islands and USA South and St Vincent and The Grenadines and St Lucia do not count towards the rankings as none of them feature two sides that are full member unions of World Rugby.

The World Rugby Rankings update every Monday at 12:00 UK time.