From the electrifying speed of Aaron Smith's distribution in the 2015 World Cup-winning All Blacks, to Antoine Dupont leading France, the No 1 team in the world, sides are shaped by the men wearing the No 9 jersey.
Because a halfback handles the ballmore than anyone else, their style decides the tempo of a game. As a prime example of the radical difference a halfback can make, take Ireland in this year's Six Nations.
For a decade Conor Murray was the first choice for Irish coaches, most notably Joe Schmidt. He's a gifted, tough, wily player, whose game is one that grinds the opposition down, feeding one-off runners, running himself, or lofting beautifully-judged high kicks.
There's been a big change in Ireland's style since Andy Farrell took over as head coach for the 2020 Six Nations, and at the heart of the more attacking feel is New Zealand-born Jamison Gibson-Park. His move to Ireland in 2016, after being in the Hurricanes' Super Rugby-winning team, has paid off for both him and the Irish.
Gibson-Park is 30, but he has the energy and quickness of a 20-year-old. His ability to be snapping at the heels of the forwards at breakdowns, and the alacrity with which he then fires the ball to his runners has won him man of the match awards in Six Nations, and freed up dynamic attackers for Ireland, like centre Robbie Henshaw, and another Kiwi import, wing James Lowe.
As the All Blacks look towards the World Cup next year we may be seeing a pairing at the Highlanders of Aaron Smith and Folau Fakatava that could share the load at halfback, and offer between them lightning distribution like Gibson-Park and a similar work rate to Dupont.
What first caught the eye of Jamie Joseph, when Smith left his job at the Cut Loose hairdressing salon in Feilding to go to Dunedin in 2011 was how the Manawatū man, who had slipped through the Blues' fingers in 2010, set a backline flying with how quickly he cleared the ball.
Fakatava presents a slightly different skillset. He's not a slouch with his pass, but as he's shown with his stellar efforts for Hawke's Bay, he's especially dynamic at breakdowns. It won't have escaped the All Black selectors' attention that he's a master of the jackal, which is legally wrestling the ball from an opponent after a tackle.
He's been a star runner since he came to New Zealand from Tonga as a 16-year-old, and played for the remarkable Hastings Boys' High School First XV of 2016 and 2017 that beat giants of the school game, winning the national title in '17.
In December, when he'll turn 23, Fakatava will be eligible for the All Blacks, and Super Rugby next year will be the chance for him and Smith to demonstrate again how well they work in tandem.
If Smith starts at the 2023 World Cup, you can see how introducing Fakatava, with his power and eye for a gap, later in a game might echo the huge success of 2015, when Beauden Barrett was subbed on as a fullback in the quarter-final, semifinal, and final, to devastating effect, tearing weary and sometimes slightly disorganised defences to shreds.
It wouldn't be the safest, most obvious option, but if you go right back to the first All Blacks World Cup victory in 1987, two players made their test debuts at the Cup, fullback John Gallagher and flanker Michael Jones. Gallagher lit up the All Blacks and the tournament with his flair. Michael Jones? He was so good there's a statue of him at Eden Park.
Thinking outside the square can work, even at the highest levels.