China's Xu, the favourite going into the event at Carioca Arena 3, suffered what appeared to be a lower back injury in her semi-final win over Logunova’s compatriot, Olga Kochneva, and seemed to have limited movement in a final that ended 5-3 in her opponent’s favour.

Victory earned a first Grand Prix title of the season for experienced Russian Logunova, a two-time Olympic team gold medallist, who had to settle for bronze in Qatar and Hungary.

"I’m very happy and I hope to see you again in Rio at the Olympic Games," said the 35-year-old.

"My coach said if you are not sure what to do, stay passive, and get your touches that way."

Kochneva, the world number 46, achieved her best result to date by securing a bronze medal along with the other losing semi-finalist, Katrina Lehis of Estonia.

The Russian had dispatched the world number 13 Choi In-Jeong of South Korea in the last-32 and world number five Emese Szász of Hungary in the last-16. 

Other surprise results included early defeats for world number two Rosella Fiamingo of Italy against China's Sun Yujie and world number three Violetta Kolobova of Russia against Germany's Alexandra Ndolo.

It was the final épée Grand Prix of the season for the women.

Tomorrow is due to see the men’s event take centre stage as world number one Gauthier Grumier looks to claim a second Grand Prix gold of the season and underline his status as firm Olympic favourite.

With the rest of the world’s top 10 all present in Rio de Janeiro, however, the Frenchman will most likely have to be on top form to do so.

The Rio Grand Prix is the first competition to adopt a new cross formation for the pistes, an innovation in the sport designed to provide an improved view of the action for spectators.