The biggest obstacle to Madison de Rozario’s quest to hold on to her Paralympic marathon crown may not be the cobbles that line the streets of Paris but the ruthless form of Switzerland’s Catherine Debrunner.

De Rozario has placed a high priority on going back-to-back in the French capital after securing a gold medal in the T54 event at the Tokyo Games.

But Debrunner is likely to have a big say in de Rozario’s fortunes, given the Swiss athlete has dominated the track at the Stade de France.

To date in Paris, Debrunner has won gold medals in the 400m, 800m, 1500m and 5000m, showing she’s as versatile as one of those little red knives for which her homeland is famed.

She also grabbed silver in the 100m and the only thing left for the 29-year-old to get her hands on is de Rozario’s marathon crown.

“In German we say, all the puzzle parts have come together,” Debrunner told AAP.

“This race is something completely different and I’m excited for this challenge, usually when I do a marathon I’m not doing a lot of races (in the build-up).

“Madi and I have a really good friendship, she’s the reigning Paralympic champion and she is the one who gave me the courage to believe that a T53 athlete can be successful in the marathon.”

Debrunner, like de Rozario began her career as a sprinter but has shown an ability to excel in distance racing, winning marathons in London, New York and Chicago over the last 12 months.

De Rozario has not seen an athlete like Debrunner, who has dominated so many distances at one time.

“She has changed so much as an athlete in these last three years,” de Rozario said.

“Now she’s dominant across the board - she’s aggressive and smart and knows her strengths.

“In women’s racing, we didn’t have a Catherine until now, someone who races so assertively.

“You have to change your race plans because you’re beside her because she’s such a unique athlete.”

De Rozario has had limited chance to test out her race chair on cobblestones and has been keen to underline the challenges that the bumpier surfaces can throw up.

As Debrunner goes in hunt of a sixth medal from Paris it’s worth pointing out that she does most of her training in the Netherlands, where the roads are often paved with cobbles.

“But not 5km of them,” the Swiss said.

“I’ve had a little bit of practice.”