In July 2011, Robin Soderling smiled broadly and held aloft the Swedish Open trophy in front of his home fans. He was the world No 5 - the best of the rest outside the 'Big Four' - and at the age of 26 had time on his side to go one better than his two French Open finals and win a first grand slam.

“But that match was the last I ever played,” Soderling says, seven years on. “After that I didn’t leave the house for six months.”

Soderling, it turned out, had been playing for much of 2011 with an acute case of glandular fever, which became so debilitating that soon after winning the Swedish Open he could barely get out of bed. Soderling then spent almost four years trying to make a comeback but could not fully shake off the illness and officially retired in December 2015.

Soderling’s legacy though remains undimmed, largely because of the events at Roland Garros nine years ago. On a gloomy Sunday, Soderling - a provocative and divisive presence on the Tour - did what had never been done, and has remained almost unthinkable since: he beat Rafael Nadal at the French Open.

Nadal's near-perfect record since - just one defeat, against Novak Djokovic in 2015, and six more titles - has made Soderling’s achievement even more remarkable. Nadal is also the huge favourite to pick up an 11th title at this year’s tournament, which begins on Sunday.

Soderling celebrates beating Rafael Nadal at the French Open in 2009 credit: Getty Images

In the years when Soderling was convalescing and dreaming of a comeback, he could not bring himself to watch the event - even on television. Now though, he is more contented and will be at Roland Garros this year.

Still young - at 33, he is three years younger than Roger Federer - healthy again and with that glint in his eye and impish smile, Soderling is enjoying a busy retirement. He runs his own tennis equipment business RS Tennis, coaches the exciting Swedish youngster Elias Ymer and is a dad to Olivia (five) and Fred (three).

His career may have been cruelly cut short, but in those dark days of 2011 and 2012 all Soderling wanted was to feel well again.

“I was really sick,” he says. “I was in bed with cold sweats, all different symptoms. It was really terrible for a long time, and when the fever went away there was all this weakness and tiredness.

“Then after a few years I felt good in daily life but as soon as I started to push my body the symptoms came back and I had no strength at all. I got so tired. After an easy practice session all I wanted to do was sleep for days.

“For a long time I couldn’t even watch tennis on TV because I missed it too much. I was bitter and upset because it didn’t seem fair. I was young and it was tough to see players that I played against my age, even older performing well. Like [Stan] Wawrinka and I are almost the same age.

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“When I retired it became easier, and every month that passes it gets easier because there are less players my age. Now I’m too old anyway so I don’t have to think about it too much.”

With a bit of distance from his retirement, Soderling is better able to look back fondly at his many achievements, which include a world ranking of No 4, two grand slam finals and 10 titles.

And though he actually regards beating Federer at the following year's French Open as an equally good, if not better, performance, Soderling will also always have that 2009 win over Nadal - one of tennis's "Where were you when?" moments.

The seeds of the upset were sown two years earlier at Wimbledon when Soderling riled Nadal in a tetchy third-round match. Soderling celebrated a dead net cord, didn’t look Nadal in the eye when they shook hands, and most humiliatingly of all impersonated the Spaniard’s habit of fiddling with his shorts in front of a disbelieving Centre Court.

Nadal was furious, and Soderling says now that he may have gone too far with his antics. But he stands by making it clear that he was not overawed by Nadal.

Two years later at Roland Garros, Soderling was similarly fearless: “I remember I beat [David] Ferrer in the third round and the first question the journalist asked me was ‘do you think Rafa will win the French Open again this year?’.

Soderling reached two French Open finals credit: Getty Images

“At that moment I realised no-one believed I could win. At least I had to otherwise there was no point going on court.

“So I told myself I have a chance, I just have to focus on my game. When I got on court I felt really confident, really good but I also felt like there was no pressure. No-one expected to me to win so I tried to see it as there’s only an upside.

“To beat Rafa on clay, especially in best of five sets you have to be aggressive and dictate the points. That’s how I played naturally so it was maybe a bit easier for me. But I also tried to be a bit more aggressive than normal and also take a few more risks, and that day it really worked.”

Soderling stresses that to win against Nadal or Federer you must have self-belief, which he feels is lacking in too many of today’s players.

“I get the feeling even guys in the top five don’t really believe,” he says. “They’re there to see what happens. Their focus is just to go off the court with their head high - you can see it even in the warm-up. It means the big guys win many matches before they have even started.

“You have to unsettle these guys and stand up for yourself. Show your opponent that you believe in yourself and you’re there to win.”

So is that the way to beat Nadal at the 2018 French Open? "Yes", Soderling responds. "Do that, play aggressive...and then hope for the best."