7 must-watch moments during the Rio Olympics

By Nick Murray, CBC Sports

Beyond the headlines about polluted water, infrastructure problems and doping, the Rio 2016 Games are sure to give sports fans some unforgettable moments.

• FULL SCHEDULE: Rio Olympics

Here are a few to watch for:

Michael Phelps' swan song

The most decorated Olympian of all time will lead Team USA during today's opening ceremonies, and with it, begin his fifth Olympics which he insists is his last.

Though he called it quits after London 2012, this time around Phelps said he's embracing the experience, which could draw some goosebumps for both Phelps and fans if he genuinely plays into his goodbye from Olympic competition.

• Michael Phelps determined to go out on his terms

The 22-time Olympic medallist – 18 of which are gold – will compete in the 100m butterfly and 200m butterfly, both of which he holds the world record. He's also slated to swim in the 200m individual medley, and will likely swim in the 4X100-metre freestyle relay.

Adding to the drama, Phelps will be going for four-peats in the 100 fly and 200 individual medley.

Usain Bolt eyes trifecta for 3rd-straight Olympics

The world's fastest man is his confident self going into Rio, proclaiming he's "not going to lose one of those golds, for sure."

If he follows through, Usain Bolt will be the only athlete to ever achieve an Olympic three-peat in the 100- and 200-metre events.

• Usain Bolt: Track and field 'needs me to win' at Rio Olympics

The sprinter says he expects Rio to be his swan song, too, but the soon-to-be 30-year-old still has some gas left in the tank.

Bolt ran the 100 in 9.88 seconds in Jamaica two months ago – to put it into perspective that's the same time U.S. sprinter Ryan Bailey ran in the London 2012 final, good for fifth – and whether or not Bolt went full tilt remains to be seen.

He also ran a 9.79 last year at the world championships in Beijing, matching Justin Gatlin's bronze medal-winning time in the London 2012 final.

Bolt could very well win three more gold medals and hang 'em up. And if in his mind he's done after his final race in Rio, it will surely be a victory lap to remember.

Brazil looks to avenge World Cup collapse

If there's one team facing arguably more pressure than any other, it's the Brazilian men's soccer team.

Following a disappointing fourth place finish at home in the 2014 FIFA World Cup, the expectation is high for this team to turn it around and win its first Olympic gold medal.

Leading the way is FC Barcelona star Neymar, but Brazil has already put itself in a tough spot, playing to a scoreless draw against South Africa yesterday. 

• Brazil's soccer team jeered after disappointing Olympic debut

Brazil still faces good odds to advance to the knockout stage with matches against Iraq and Denmark still ahead, but the road to gold just hit a speed bump.

Water woes

As we approach the opening ceremonies, we suddenly hear the Canadian Olympic Committee's medical officer say athletes don't feel the water – the same water of which we've been seeing scathing stories – will be an issue.

We won't know how bad the water is until the first event. So this memorable moment will be when the first athlete takes a mouthful of it.

Golf and rugby make their Olympic returns

There are plenty of moments brewing in golf and rugby sevens as the latter makes its debut, and the former returns after 116 years.

On the golf side, look for the women to put on a show. Not only are most of the top-ranked women golfers accounted for – unlike the men – but the Rio 2016 games will be a rare occasion where both PGA and LPGA pros compete on the same course, under the same conditions.

Look for some LPGA players to out-do their male counterparts, and make a statement for women's golf.

On the rugby side, Australia's women's team may be this season's World Rugby Sevens Series champs, but Canada had the last laugh in May, beating the Aussies to capture the Clermont-Ferrand title.

Watch for Canada to make a medal run in the inaugural Olympic tournament.

Will Brazil's beach volleyball dominance continue?

If there's such a thing as a sure bet, it's Brazil winning a beach volleyball medal on home soil.

Since the game's Olympic debut in 1996, Brazil has never failed to earn a beach volleyball medal – only the 1996 men and the 2008 women's teams failed to win climb the podium.

Russian ban creates opportunity for others

With more than 100 Russian athletes being banned from competing over the next few weeks, it certainly opens the door for other athletes to reach the podium, and arguably none more-so than in women's pole vaulting.

• Rio 2016: 5 Russian stars who could miss Olympics

Two-time Olympic champion and world record holder Yelena Isinbayeva is among Russia's banned athletes. So watch out for Greek pole vaulter Ekateríni Stefanídi to emerge as a darkhorse contender for a medal, fresh off a win at the European Championships last month.