Canada's women beat Great Britain 9-6 in a tight encounter on the third day of women's curling at Sochi 2014.
British skip Eve Muirhead, with her team 8-6 behind, missed a high-risk, all-or-nothing shot at the death which handed Canada victory.
"I don't go for shots if I don't think they are there. We had a good chance in that last end," said Muirhead, whose team have won one of their three ties.
GB's men comfortably overcame Switzerland 4-2 in their fourth match.
David Murdoch's team always looked in control and they are fourth in the standings with China, Norway and Sweden unbeaten.
After Canada's skip Jennifer Jones missed a relatively straightforward chance to win, Muirhead had been presented with a choice for her final shot.
The 23-year-old could have played it safe, scored two and taken the game to an extra end (in which Canada would have had the advantage of the final stone, known as the hammer).
But she attempted to clear all of the Canadian stones from the house for three and victory, only to see the gamble fail to pay off.
"It was a high-quality game, and Jennifer played fantastic," added Muirhead. "When you go three down against a high-quality hitting team like Canada you are always going to be chasing the whole game."
The GB women, currently joint seventh, have six round-robin games left, all against lower-ranked opponents.
They need a top-four finish to make the semi-finals. Switzerland and Canada are the two unbeaten teams to date.
The men's total of six points scored equalled the lowest tally in a men's Olympic curling match, a tally set in 1998 when GB defeated Norway 4-2 and equalled when they beat United States by the same scoreline in 2010