Thiago Pereira says he is living "a unique dream," competing at his home Olympic Games as one of the country’s favourite athletes.

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And there is only one conclusion to his dream: he wants to beat Michael Phelps, the man he considers the greatest Olympian of all time.

The 30-year-old Pereira, known throughout Brazil as 'Mr Pan' thanks to his record haul of 23 Pan American Games medals, has been fighting losing battles with the great USA swimmer for 12 years at three Olympic Games.

The only time he can remember defeating the 22-time medallist was at London 2012 when he took silver in the 400m individual medley behind US threat Ryan Lochte who, that night, delivered a career-defining performance that relegated Phelps to an unaccustomed fourth-place finish.

"We’ve raced together since 2004. Me, Ryan and Michael, all those worlds and Olympics,” Pereira said poolside at the Olympic Aquatics Stadium.

"One of the reasons I’m still motivated, still believing, as I go into my fourth Games is Michael and Ryan. Those guys have pushed me to still be here.

From right to left, Thiago Pereira, Michael Phelps and Ryan Lochte dive into the water at Beijing 2008  (Photo: Getty Images/Al Bello)

"I believe Michael’s changed the way people think about swimming. He’s motivated people to think differently about the sport, given it a big profile. And that’s what we want.

"In my eyes, he’s the greatest Olympian of all time. I had that opportunity to beat him once but I respect him for everything he’s done. As a swimmer, I know how hard it is to hold yourself at this top level for so long. He is an extraordinary athlete."

Phelps will be going for a fourth successive individual triumph in both the 100m butterfly and 200m individual medley — a feat never achieved in any swimming event — but it is the latter event in which Pereira hopes to derail the great champion's fifth (and possibly final) Olympic Games.

"Since London 2012, I’ve had the best four-year cycle of my career. I’m pretty sure I’m in the best shape I’ve ever been," said Pereira, who won silver in the 200m individual medley behind Lochte at the world championships in Kazan, Russia, last year.

"I’ve eaten well, rested well, trained well. I’ve done everything I could to be on the podium again."

Pereira carries the flag at the Toronto 2015 Pan Am Games (Photo: Getty Images/Ezra Shaw)

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Tipped as the best of the host nation’s medal chances in the pool, Pereira is buoyed by competing in his home state, as he hails from Volta Redonda, just an hour away from the city of Rio de Janeiro.

“For me, this has been more than unique. I’ve had the chance in 2004 to start my Olympic career in the place where the whole history of the Games started and now I’ve the chance to compete in my own country. Most athletes don’t ever get this chance so I feel great.

"I hope these Games will change the way we think about sports in Brazil. I’m pretty sure it’s going to be amazing and we’re all hoping the whole of Brazil can put on the best Olympic Games in history.”