At last year's championships in Fukuoka, the young Tunisian edged American Bobby Finke in an epic battle for the 1,500m title, threatening Sun's 14.31.02 record set at the 2012 London Olympics.
Hafnaoui's 14:31.54 swim stands as the second fastest in history and the world record appears at the 21-year-old's mercy.
Perhaps not at Doha, though.
"I don't think so ... Me and my coach just decided to treat it as a preparation meet. All the focus right now is just for Paris," he told reporters at the Aspire Dome on Saturday. "Nothing more."
In 2021 at the age of 18, Hafnaoui stunned the world by winning the 400m freestyle gold from lane eight at the COVID-delayed Tokyo Olympics after being the slowest qualifier in the final.
After taking time out of the pool to study in 2022, Hafnaoui returned with a bang last year, claiming the 800 and 1,500 world titles at Fukuoka and silver behind Australia's Sam Short in the 400.
A hero in his home nation, Hafnaoui is now based in California under the watch of former U.S. team head coach Mark Schubert, who runs an elite distance programme in Orange County.
Hafnaoui's bid to sweep the 400-800-1500 treble will be one of the highlights of Doha - and his chances are good.
Short and Finke, the third fastest swimmer of all-time in the 1,500, have both skipped the meet.
Hafnaoui will be straight into action on day one on Sunday for the 400 which boasts a strong field despite Short's absence.
The German Fukuoka bronze medallist, Lukas Maertens, and Australian former world champion Elijah Winnington are set to race along with Irish sensation Daniel Wiffin, who smashed Grant Hackett's short course 800m world record at European championships in December.
Hafnaoui's success has followed in the wake of Tunisian trailblazer Oussama Mellouli, the first African man to win an individual Olympic swimming gold when he clinched the 1,500m title at the 2008 Beijing Games.
Mellouli also claimed history with gold in the 10km at London, becoming the first swimmer to win Olympic medals in both open water and the pool.
Hafnaoui said he hoped one day to be counted among the greats of distance swimming and that he might emulate Mellouli by adding open water to his programme after Paris.
"Mellouli is everyone's hero (in) Tunisia," he said.
"Everyone is looking (up to) him.
"We're going to take a break after Paris and just, like, (do) brainstorming and see what opportunities I have right now."
