The IAAF’s announcement that this year’s World Relays will include a 2x2x400m mixed relay has generated reactions ranging from bewilderment, to excitement, to mild terror from the track and field community. The never-before-seen event has been derided for its difficulty, and for the simple fact that demand for such a relay was seemingly nonexistent. And yet, no one can deny the 2x2x4 — where two athletes will alternate 400m legs — will be a fun and entertaining spectacle for a sport that could always use more of that.

The strategy of picking two athletes capable of running two 400m legs in the span of a less than a minute will be fascinating. Will two 400m runners work best in this scenario, or will two 800m athletes be a better alternative? What about a combination of both? The relay selection will force each team to answer a question that they have never before been asked: is speed or endurance more important in a two-person, four-lap race? No one knows as of yet, and that’s why the track community is currently buzzing.

While we don’t know yet who will serve as the 2x2x4 guinea pigs come May in Yokohama, Japan, many countries could build tantalizing two-person teams if they so choose. Below, we’ve ranked the top potential duos in the world.

1. South Africa - Wayde Van Niekerk and Caster Semenya

The 400m world record holder and the most dominant 800m runner of this era would no doubt make for a lethal combination; one could argue that the 2x2x4 was designed specifically for the speed of Wayde Van Niekerk and the speed endurance of Caster Semenya. This is the ultimate unstoppable dream team.

2. USA - Michael Norman and Ajeé Wilson

The Americans could certainly field a competitive team with just their 800m corps, as either Clayton Murphy or Donavan Brazier would couple well with 800m American record holder Ajeé Wilson. But I like a team with speed and strength. 43.61 man Michael Norman and Wilson would present a challenge to Van Niekerk and Semenya.

3. Kenya - Emmanuel Korir and Margaret Wambui

The Kenyans don’t have any elite 400m runners at their disposal, but the 1:42 speed of Emmanuel Korir and Margaret Wambui’s 1:56 PR makes for a viable threat if a rival 400m specialist falls apart on their second leg. Plus, Korir has a 44.21 400m to his credit, giving him the best leg speed of any half-miler in the world.

4. Jamaica - Akeem Bloomfield and Natoya Goule

Just like my two top-ranked teams from South Africa and the U.S., the Jamaicans would roll out a male 400m ace and a female 800m national record holder with Akeem Bloomfield (43.84 PR) and Natoya Goule (1:56.15 PR). This is a daunting duo, but the three squads above are filled with more accomplished individuals.

5. Bahamas - Steven Gardiner and Shaunae Miller-Uibo

The Bahamas doesn’t have the luxury of a mid-distance star, but Olympic gold medalist Shaunae Miller-Uibo and 19.75/43.87 man Steven Gardiner are a tantalizing duo on paper. However, picking this pair is a big roll of the dice, as speed only matters so much for athletes who haven’t proven they can excel beyond a one-lap race.

6. Botswana - Nijel Amos and Amantle Montsho

The Botswanans would be handcuffed by having the weakest female 400m specialist in Amantle Montsho (50.15 SB in 2018), but Nijel Amos and his reckless approach to racing seems fitting for a competition like this.

7. France - Pierre-Ambroise Bosse and Rénelle Lamote

The French would be big sleepers, but the 2017 800m world champ Pierre-Ambroise Bosse and 1:58 runner Renelle Lamote combine to form one of the best half-miler duos on this list.

8. Great Britain - Jake Wightman and Laura Muir

The Brits would also likely take a purely mid-distance approach to this relay, and Laura Muir and Jake Wightman are the two ideal candidates to form their squad. Muir is world-class from 800m to 5,000m, so there is no fear of her hitting the wall on the second leg, while Wightman has a similar profile with elite PRs in the 800m and 1,500m. Without a sprinter, however, Team GB would likely have to rally significantly in the second half.

Other potential teams: Poland - Adam Kszczot (1:43.30 PR) and Justyna Swięty-Ersetic (50.41 PR); Canada - Brandon McBride (1:43.20 PR) and Melissa Bishop (1:57.01 PR)