While Bolt has already called time on his injury-plagued season, the 32-year-old Gatlin, the 2004 Olympic gold medallist in the 100m and 200m world champion in 2005 before serving a four-year doping ban, has seized his opportunity to dominate global sprinting in 2014.
The American veteran has set the fastest times of the year in both sprints, 9.80 in the 100m and 19.68sec in the 200m.
He will have Bolt's King Baudouin stadium best of 9.76sec over the 100m in his sights, but will be racing a formidable field that includes the Jamaican trio of recently-crowned Commonwealth champion Kemar Bailey-Cole, former world record holder Asafa Powell and Nesta Carter, Briton James Dasaolu and US teammate Tyson Gay.
In the field, it is fitting that the men's high jump gets a show-in at the 14th and final Diamond League meet of the season.
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The event has flourished in 2014, and Brussels will see Ukraine's world champion Bohdan Bondarenko, Olympic champion Ivan Ukhov of Russia and Qatar's world indoor champion Mutaz Essar Barshim all in action.
Barshim recently cleared 2.42m to match Bondarenko's best, while Ukhov has cleared 2.41. With both Ukrainian Andriy Protsenko and Canadian Derek Drouin having also gone clear at 2.40m, competition promises to be tight.
Back on the track, French steeplechaser Mahiedine Mekhissi is looking for revenge in his favourite event after being disqualified at the European Championships in Zurich for taking off his shirt when entering the finishing straight.
Mekhissi will seek to break the European 3000m steeplechase record and become the first European to break the 8-minute mark, with only 10 athletes in track history having ever run the 3000m steeplechase under that time.
There will be a host of other stars from the European championships on show, notably Dutch double sprint gold medallist Dafne Schippers and 1500m champion Sifan Hassan, racing the 200 and n800m respectively.