GANGNEUNG, South Korea—This is an Olympics that has seen the phrase “curling doping scandal” become a thing, and yet somehow that isn’t even the most shocking development this week in the world of rocks and brooms.

As surprises go, not even a Russian curler’s positive drug test tops this: Canada, the country that loves curling and dominates it like no other, is on the brink of elimination from the women’s tournament.

The defending champions, medalists at every Olympics since curling was added to the Winter Games in 1998, need two wins on Wednesday. And that’s just to advance to a tiebreaker to get out of the round-robin phase.

“Unthinkable,” said Mike Harris, a member of Canada’s silver-medal men’s curling team at the 1998 Olympics.

“I can’t even fathom it,” said Colleen Jones, a retired Canadian curling star who led two women’s world championship teams.