World and Olympic 800 metres champion Caster Semenya will step down a distance to take on the Olympic 400m gold medallist Shaunae Miller-Uibo at the tenth International Association of Athletics Federations (IAAF) Diamond League meeting of the season in Rabat tomorrow.
The showdown is expected to be an intriguing highlight of the event in Morocco's capital at the Prince Moulay Abdellah Stadium.
Miller-Uibo, from The Bahamas, has a best this season of 49.77sec and recorded 49.86 in Budapest 11 days ago.
South Africa's Semenya set her 50.40 lifetime best in Brussels last year and has a season’s best of 51.60 from early April.
The field also includes Quanera Hayes, who clocked 49.72 to capture the American title less than three weeks ago.
Similarly, the men's 200m will bring together the fastest 100m runner this year, Canada's Olympic bronze medallist Andre de Grasse, and the fastest 400m runner of the season, former US college athlete Fed Kerley, making only his second professional appearance.
Olympic 200m silver medallist De Grasse, who clocked 9.69 in Stockholm with plus 4.8 metres per second of wind assistance, and Kerley, whose clocking of 43.70 put him seventh on the all-time 400m list, will meet in the middle as they face the man who set a personal best of 19.85 in Doha before winning this year's USA Track and Field World Championships trials, Ameer Webb.
Elsewhere, the Rabat stop-off will be critical to the men's and women's Rio 2016 3,000m steeplechase winners, Kenya's Conseslus Kipruto and Bahrain's Ruth Jebet, as they seek to get back on track in good time for next month's IAAF World Championships in London following recent setbacks.
Kipruto, who leads this year's rankings with a time of 8min 04.63sec, returns to action for the first time since winning the Kenyan World Championship trials last month following a minor injury.
The race features one of Morocco's rising talents, 21-year-old Soufiane El Bakkali, fourth at Rio 2016 and might provide his home crowd at the Meeting International Mohammed VI d’Athletisme with plenty to shout about.
The home runner knocked almost ten seconds off his previous best in clocking 8:05.17 behind Kipruto at last month's IAAF Diamond League meeting in Rome, and has since won at the Stockholm Diamond League.
In the women's race, Jebet should have a relatively straightforward chance to get back to winning ways after finishing fourth at the Paris IAAF Diamond League meeting, where she set out hoping to better the world record she had set in the French capital the previous year before coming to grief in a fall at the water jump with three laps remaining.
Similarly Colombia's Olympic triple jump champion Caterine Ibarguen will have the chance to regain the winning habit against a field that includes some estimable rivals, including Olga Rypakova, the Kazakh athlete who beat her to the London 2012 title.
Ibarguen will not be challenged by the 21-year-old who beat her in Rome this year, Yulimar Rojas of Venezuela.
There is work to be done also by another Rio 2016 champion, Brazil's pole vaulter Thiago Braz, who needs to improve upon his modest season's best of 5.60 metres with London 2017 in the offing.
Rio 2016 silver and bronze medallists Renaud Lavillenie and Sam Kendricks, of France and the US respectively, are already operating at a significantly higher level.
At the moment the class of the field is Pawel Wojciechowski, Poland's 2011 world champion who improved his national record to 5.93m in Lausanne nine days ago.
Like Braz, Canada's Shawn Barber, the defending world champion, will also be looking for a performance better than his 5.71m season's best.
But there have been no upsets or alarms for another Rio 2016 champion, US shot putter Ryan Crouser, who will be looking for his 10th straight victory in Morocco, having reached 22m or better in six of his seven 2017 competitions.
Jamaica's Olympic 100 and 200m champion Elaine Thompson, concentrating on the shorter sprint this year, will seek her 14th straight win.
Thompson has the world’s fastest time of the season, 10.71, to her credit, and arrives at Rabat having won the London IAAF Diamond League 100m in 10.94 despite having to run in shoes with barely any spikes in order not to exacerbate an Achilles tendon problem.