Ireland successfully began their bid for back-to-back Grand Slams, England ended their opening game curse and Scotland held on to deny Wales a stunning comeback victory.

So what are the key talking points from the opening round of the competition?

Ireland eye back-to-back Grand Slams

No side has ever won back-to-back Grand Slams in the Six Nations.

Ireland's record away win against France showed why this should be talked about as a realistic possibility this year.

Andy Farrell's side were near perfect in Marseille as they banished any potential World Cup hangover following their agonising quarter-final defeat by New Zealand.

Leinster's Joe McCarthy picked up the player-of-the-match award on his Six Nations debut, announcing himself as one of the most physical locks in the world.

The 22-year-old made three dominant tackles and got over the gain-line with 83% of his carries.

"Every team in world rugby needs an enforcer in their pack. England typically had it in Courtney Lawes," former Wales captain Sam Warburton told Six Nations Rugby Special.

"McCarthy could be a revelation for Ireland."

A favourable draw, with three games in Dublin and Italy next up, puts Ireland in pole position to create more history under Farrell.

For Italy, a three-point defeat by England offers much improvement after they conceded 22 tries in their final two pool games at the World Cup.

But facing a rampant Ireland in Dublin is an altogether different prospect, which may hinder their progress after an encouraging start to the championship.

France miss superstar Dupont

Antoine Dupont's announcement that he would miss the Six Nations to pursue his ambition of playing for the France Sevens team at the Olympics was shock to everyone.

Their captain, most creative and best player is at the centre of everything good about French rugby.

The 27-year-old played at fly-half for Toulouse this weekend before heading off to Sevens camp. Two sublime try assists showed how badly he was missed in France's defeat against Ireland.

"Most people focus on the breaks or passes or support lines that he does, but the basics of Dupont's game are so many levels above even your international standard player," former England wing Chris Ashton told the Rugby Union Daily podcast.

"He is so efficient and gets you out of tight spots."

His replacement Maxime Lucu struggled to recreate the unpredictability of Dupont in Marseille, prompting the question of whether France cope without their star player.

France, who played the majority of the game against Ireland with 14 men after lock Paul Willemse was sent off for two yellow cards, will look to bounce back against Scotland at Murrayfield on Saturday.

England's new defensive system will take time

Kevin Sinfield was the man in charge of England's defence when Steve Borthwick took over as head coach.

The rugby league legend had mixed results and his duties have now been taken on by Irishman Felix Jones.

The 36-year-old Jones has already been part of two successful World Cup campaigns with South Africa, putting in place and fine-tuning their successful blitz defence.

England played with the high line-speed that the blitz defence requires but Italy exploited a lack of familiarity with the system to score three times.

"I have coached and played in changing systems and it takes a while to become instinctive," former England fly-half Paul Grayson told the Rugby Union Daily podcast.

"There is nothing wrong with the system. It is just having enough miles on the clock and knowing the players well enough for it to be instinctive to do the same thing at the same time."

South Africa's World Cup-winning coach Jacques Nienaber said it took 14 games for the Springboks to adjust to the system when he joined Rassie Erasmus in the leadership group in 2018.

In that time they lost 50% of their games. But South Africa only lost once in 2019 and won the World Cup.

England will need to tighten up their new defence when they host Wales on Saturday, who scored four tries against Scotland and demonstrated an ability to exploit the wide channels.

Gatland needs new strategy to let youth shine

When Duhan van der Merwe cruised around Tomos Williams to score Scotland's third unanswered try in Cardiff, the game looked over.

But 27-0 down, Wales cut loose with their young and fearless squad falling just short in a pulsating 27-26 defeat.

The key difference was a move away from their conventional direct and physical 'Warrenball', which has been so successful over the last two decades for coach Warren Gatland.

Instead, it was all about running rugby, with replacement half-backs Williams and Ioan Lloyd injecting pace in the second-half revival.

"It is not too much about selection but strategy," former Wales international Philippa Tuttiett told the Rugby Union Daily podcast.

"In the second half you saw more of a gameplan which suits the young players and you saw them feed off that and grow in confidence."

Wales travel to Twickenham on Saturday needing to start the way they finished against Scotland.

Russell stars but Scots discipline costly

The self-proclaimed Lionel Messi of rugby.

When Scotland click in the Six Nations, Finn Russell is at the heart of it. The Bath fly-half produced two try assists for Van der Merwe to help the Scots race into a 27-0 lead just after half-time.

The first a loop play, the second a wonderful offload - Russell was in complete control. Added to a faultless display off the tee, he was having fun in Cardiff.

"Finn Russell was in flow state. Just floating and putting people in space and playing in all parts of the pitch," former Scotland international Andy Nicol told the Rugby Union Daily podcast.

However, Scotland's new captain was disappointed with his side's discipline in the second half, with two players being sent to the sin-bin as the visitors lost control.

Wales gave away four penalties in the whole game - their last on 26 minutes - compared to Scotland, who gave away 14 consecutive penalties.

"The problem was discipline," former Scotland captain John Barclay told Six Nations Rugby Special.

"When Scotland are good they are good, but it doesn't matter if you are ill-disciplined."

Gregor Townsend's side started last season's campaign with two wins from their opening games and will look to do the same against France on Saturday.

Player of round one - Joe McCarthy

The standout second row in Ireland's victory over France, McCarthy topped the stats for most metres per carry, gain-line success, dominant tackles and defenders beaten.