A first-ever Olympic loss for gold medal-winning Canadian curlers Kaitlyn Lawes and John Morris proved no serious stumbling block as the duo emerged in first place from the round-robin stage of the mixed-doubles tournament on Sunday.

Following a tournament-opening loss to the Norwegians, the Canadians proceeded to barrel through their remaining competition, amassing a 6-1 record and outscoring their final six opponents 46-17 en route to the top seed for the knock-out round starting on Monday.

"We knew coming into this that mixed doubles would be incredibly difficult to come out of the round robin without a loss, and that happened to be our first game, but we didn't let that bother us," Lawes said. "We wanted to learn from that game and continue to build momentum as we went on."

Lawes and Morris have won separate golds in Olympic curling. She won with the Canadian women in Sochi in 2014 and he won with the men in Vancouver in 2010, and neither had previously lost in Olympic competition.

Mixed-doubles curling is making its debut as an Olympic event here at the Pyeongchang Games. A faster-paced game than traditional single-sex curling, teams of two - a female and male - complete up to just eight "ends" as opposed to 10, and there is no shot-calling "skip" as in the four-player version.

Called the "roaring game" from the rumbling sound the 20kg (44-pound) polished-granite stones make as they slide over the pebbled ice sheet, curling is believed to have its origins on frozen ponds in medieval Scotland.

Long dominated by Canada and northern European countries, it is the world's fastest-growing winter sport, with countries such as China ranking as emerging powers.

China's Rui Wang and Dexin Ba delivered in a win-or-go-home game on Sunday morning, beating Norwegians Kristin Skaslien and Magnus Nedregotten 9-3 to earn a rematch against them later in the day for the final spot in the semi-finals.

"These guys have been in a must-win situation for some time now," Chinese coach Marcel Rocque said.

The Chinese dropped three of their first four games but then finished with a three-game winning streak to force the tie-breaker, set for Sunday night.

"I kind of like that we're playing better now than we were in the beginning," said Rocque, who is Canadian. "This is where it matters."

Others progressing to the semi-finals include Anastasia Bryzgalova and Alexander Krushelnitskiy from Russia and reigning world champions Jenny Perret and Martin Rios from Switzerland.

The Swiss, too, were on the bubble but beat the Russians 9-8 on Sunday to secure the second seed, with Perret delivering a 3-point-scoring final shot to secure a come-from-behind win.

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