Olympic wake-up call: COVID-19 scare in track, plus impressive performances by Canadians

A two-time world champion at the Olympics tested positive for COVID-19 — and showed how the ripples of a positive test can affect the Olympic dreams of other competitors. 

American pole vaulter Sam Kendricks was pulled from competition on Thursday after his positive result.

It was a scare for Australia's track and field team. Since one of their athletes trained alongside him, all 63 team members headed into isolation and waited for their own test results, according to media reports — just one day before some events were scheduled to start.

At the time of publishing, the athletes had been reported as cleared.

Here's more of what you missed on Thursday in Tokyo.

Another Canadian record

The Canadian women's 4x200-metre freestyle team swam to fourth place on Thursday, and secured a new national record. 

Summer McIntosh, Kayla Sanchez, Rebecca Smith and Penny Oleksiak raced to the finish in a swift seven minutes 40.33 seconds but weren't able to crack the podium.

CBC Sports reporter Devin Heroux has more on Canada's great performance and battle for medals in the pool. 

China took the gold with a world record-setting swim, while the Americans — anchored by Katie Ledecky — won silver. 

That same day, McIntosh hit the pool again for 800-metre freestyle heats —  and the 14-year-old out of Toronto swam a personal best. 

Canadian judoka Shady El Nahas also had an impressive run in the men's 100-kilogram division.

The 23-year-old from Mississauga, Ont., emerged with a win from the repechage to move into the bronze-medal match, but fell to two-time world champion Jorge Fonseca of Portugal. The Canadian finished in fifth place. 

Canada's medal on Thursday came earlier in the day, just before the sleeping hours. Rowers Caileigh Filmer and Hillary Janssens captured bronze in the women's pair event. The women's eight will race for a medal on Friday.

Rugby 7s, basketball action

Canada's women's rugby sevens team burst out of the gates against Brazil on Thursday, defeating them in their opening game by a score of 33-0. 

But their second match was much tougher and ended in a 26-12 loss to Fiji. 

The Canadians won the first bronze Olympic medal in the sport in Rio 2016 and want to claim a spot on the podium again. Keyara Wardley and Charity Williams both left the match against Fiji with injuries.

The Canadian women's basketball team, coming off a close loss in their opening game against Serbia, came back to trounce South Korea 74-53.

CBC Sports reporter Jamie Strashin has more on Canada's domination on the court and the much-needed victory. 

Canadian golfers also started their tournament in Japan, with Corey Conners and Mackenzie Hughes each shooting a 2-under 69 in their first round, tied for 20th and six shots off the pace.

1st canoe slalom women's champion

Australia's Jessica Fox became the first woman to win a gold canoe slalom at the Olympics. The top-ranked Australian had just won bronze in the kayak event.

She showed her mastery on the white-water rapids course in the canoe — a first at the Games for women — and exclaimed as she came through the finish.

Her dad, Richard Fox — an Olympian himself — was also working as a commentator for her win.

The second-ranked Mallory Franklin of Great Britain won silver and Germany's Andrea Herzog claimed bronze.

The canoe sprint events, where Canada is a medal threat, get underway on Aug. 2 in Tokyo.

An all-Croatian battle

Croatia will definitely win a medal in men's tennis doubles: in fact, they'll win two.

After defeating a New Zealand duo, Croatian pair Marin Cilic and Ivan Dodig will play for gold at the Ariake Tennis Park.

Their opponents? Nikola Mektic and Mate Pavic, also of Croatia. They beat their American opponents in straight sets. 

Before knowing whether their teammates would make it through to the final, Cilic said it would be a "dream come true" for the country.

"If that happens there's gonna be a huge celebration, there's gonna be a day off in Croatia. It's gonna be an amazing day for Croatian sport in general," he said.