When the stars come blazing down to earth...

He may be the man with the most number of medals in Olympic history - 22 at the last count in London four years ago with 18 of them gold - but when American swimmer Michael Phelps takes off from the blocks at Rio in his fifth Summer Games, it will mark a new beginning.

It will be the 31-year-old’s first Olympics after being treated for addiction and depression. He will be a new man, his goals have changed and his prime aim will not be on hunting for more medals.

“This time, it’s about trying my hardest, giving my all. I don’t want to live the rest of my life with any regrets,” the man known as ‘The Phenomenon’ said recently.

“It will be very interesting to see what one of the greatest athletes of all time ends up after his last Olympics.

The 31st Summer Olympics begin in Rio de Janerio on Friday (on Saturday, India time), but it is already being slammed as the worst-ever with athletes posting photos of collapsing wash basins at the Athletes Village and lack of electricity and water in some rooms.

Together with the Zika virus scare, the organisational disarray, and the Russian doping scandal, there is bound to be chaos ahead of the opening ceremony.

But once the real action begins on Saturday, the spotlight will be mainly on the stars. And there are plenty of them to watch out for. Here, we line up the best of the best.

Jamaican Usain Bolt, the planet’s fastest man ever and clearly the ‘main man’ in Rio, will be going for a golden ‘triple triple’ after winning the 100m, 200m and 4x100m relay golds at the last two Olympics in Beijing and London. Trying to stop him will be American Justin Gatlin, the world’s fastest man this year who has a dope-tainted past.

Meanwhile, Britain’s distance running great Mo Farah will be hunting for a ‘double double’ after taking the 5000m and 10,000m golds in London.

There could also be a fresh new face in the sprints with American Tori Bowie, a long jumper till 2013, who appears to be a favourite to win both the women’s 100 and 200m at Rio. She is now among the three best 100m runners in the world this year and the second best, after the Netherlands’ World champion Dafne Schippers, in the 200m.

Schippers, incidentally, competed in the heptathlon at 2012 Olympics, where she finished 11th, and at 2013 Moscow Worlds, but is now the third-fastest woman in history in the 200m.

South African Caster Semenya, who came up with some stunning times while winning the 2009 World Championships but whose gender was questioned shortly after that, could run into some controversy again for she is now at her best and is a clear favourite for the women’s 800m gold.

Away from the track, it should be worth watching American gymnast Simone Biles, who according to many could be the greatest of all time, in her debut Olympics.

The first African-American to be the all-around world champion – she won it at the last three Worlds – and along the way collected a record 10 golds at the Worlds and 14 medals overall.

And in football which had an early start in Rio, all eyes will be on superstar Neymar as host and five-time World Cup champion Brazil looks to win its first men’s Olympic gold in the sport.

The big boys of golf, an event that is returning to the Olympics after 112 years, may be missing from Rio because they are worried over the Zika virus, but it is interesting to note what the world’s No. 1 tennis player Novak Djokovic had to say about the Olympics. “We have the best players in the world participating in arguably the fifth grand slam. It's of that importance for all of us, even more, because it happens every four years,” said the Serbian who took the bronze in Beijing in 2008 and finished fourth in London after losing to eventual champion Andy Murray in the semifinal.

Some of the greats of cycling will be in action too with Britain’s Chris Froome, who won his historic third Tour de France title a few days ago lined up in Rio.

Meanwhile Malaysian Lee Chong Wei, badminton’s World No. 1, who has slipped up often when it came to the big stage – he has five world silver medals, including two in the Olympics, from Beijing and London – will be very hungry to hit gold this time. And it looks like this could be Lee’s year.

While Lee will be looking for his first Olympic gold, the record 119-member Indian team will be mainly looking at its shooters to bring the bulk of its medals, especially Asian Games champion Jitu Rai who is the among the world’s top three in the 10m and 50m pistol events, and Abhinav Bindra, who won the country’s lone individual gold at the Olympics (10m air rifle, in Beijing, 2008).

Badminton star Saina Nehwal, a bronze medallist at London, is another player capable of coming good again while PV Sindhu and K Srikkanth could spring a surprise. The men’s hockey team, after its recent run, wrestlers, tennis players and archers all hold promise.