Xu has only been selected for the team event at next month's Games, with Ma and defending champion Zhang Jike occupying the two singles slots.

But Xu, who lost to another team-mate in Fan Zhendong in last week's Japan Open final, produced a superb performance to win in seven sets over the world champion.

After taking the first two sets 11-7, 12-10, Xu lost the third 4-11 before winning a tight fifth 12-10.

Ma, making the most of his powerful forehand, won the next two games 11-7, 11-6 to set up a decided, but his left-handed opponent moved ahead despite struggling with a shoulder injury.

After applying "magic spray" during a timeout when leading 8-5, Xu hung-on to win the decider 11-9 and repeat his victory over Ma at the semi-final stage in Japan last week.

“It is always special to beat Ma Long," he admitted afterwards after adding to his victories in South Korea in 2013 and 2014.

"It gives me lots of confidence that I could do it twice in a row.

“I am now a bit nervous, as I hurt my shoulder during the match, I hope it is not too severe and I will be at full strength in Rio, where I will play the team event.”

Reigning world champion Ding Ning has been selected for one of the two women's singles spots in Rio, and showed why, beating the world number one and top seed Liu Shiwen in five games in today's final.

Liu, who will only play in the Olympic team event, was beaten 11-9, 11-13, 11-8, 11-6, 11-6.

“I played very well today, it is always hard to defeat Liu Shiwen as she is a great player," the winner said.

"I really had to fight for every point, I was determined to win; this is my last match before the Olympics, so I wanted to be able to enter the Olympic tournament as a winner.”