The U.S. women are the favourite for gold after taking six consecutive world titles and Olympic gold four years ago in Beijing.
The Canadian crew lost by just three hundredth's of a second to the Americans in a recent World Cup regatta in Lucerne, Switzerland.
"We have been getting closer and closer, but we are not thinking about the U.S. — at least I am not," coxswain Lesley Thompson-Willie said following the heats.
Crew member Ashley Brzozowicz also refuses to put the U.S. on a pedestal by declaring them the team to beat.
"It's not a rivalry," said the London, Ont., native. "We all want to win gold. You can't count anyone out."
The women will try for Canada's second medal in the boats following a silver from the men's eights Wednesday.
Rowing is Canada's best medal opportunity on Day 6.
But in a stunning turn of events, the women's doubles badminton team of Alex Bruce and Michele Li will play in Thursday's semifinals.
China, Indonesia and two South Korean teams were booted from the Games on Wednesday for trying to lose matches and gain a more favourable position in the tournament.
That put Canada back in the draw. The Toronto twosome won their quarter-final Wednesday and will face Japan's Mizuki Fujii and Reika Kawiiwa. The women's doubles final and bronze-medal match is Saturday.
The men's rowing four of Michael Wilkinson of North Vancouver, B.C., Victoria's Anthony Jacob, Will Dean of Kelowna, B.C., and Montreal's Derek O'Farrell race the semifinals, as do the women's lightweight double sculls duo of Lindsay Jennerich and Patricia Obee.
Brent Hayden is back in the water just hours after winning bronze in 100 freestyle. He'll compete in the 50-metre heats. Toronto's Martha McCabe is into the final of the women's 200 breaststroke Thursday.
Hilary Caldwell of White Rock B.C., Toronto's Savannah King and Alexa Komarnycky, Sinead Russell of Burlington, Ont., and Joe Bartoch of London, Ont., swim their heats with an eye on qualifying for the evening session.
Amy Cotton of Montreal is on the judo mat in the 78-kilogram class. The 32-year-old finished ninth at the 2004 Games in Athens.
She took up judo at age six in Cape Breton "so she would stop fighting with her brother at home," according to her Judo Canada bio. "She loved the sport immediately because of the opportunity it gave her to throw around boys."
The women's beach volleyball duo of Annie Martin of Lachine, Que., and Marie-Andree Lessard of Laval, Que., are looking for their first win after a pair of losses. They take on Italians Greta Cicolari and Marta Menegatti.
At the Weymouth sailing venue, Vancouver's Zac Plavsic is seventh in men's windsurfing and Nikola Girke of West Vancouver, B.C., ninth in the women's event as they hit the halfway point of the competition Thursday.
Canada has four other vessels in the multi-day sailing events.