Her Edmonton team lost twice on the final day of the preliminary round Thursday to finish 7-4. Canada will face Allison Pottinger of the U.S. in a tiebreaker game Friday.
Nedohin lost 9-3 to Scotland's Eve Muirhead and 6-5 to Italy's Diana Gaspari. Neither country was in playoff contention at that point.
Sweden's Margaretha Sigfriddson, Switzerland's Mirjam Ott and South Korea's Ji-Sun Kim had 8-3 records and ranked first to third respectively.
The tiebreaker winner claims the fourth and final playoff berth and meets South Korea on Saturday afternoon in a Page playoff game.
Sweden and Switzerland meet in the Page playoff between the top two seeds Friday. The victor advances to Sunday's final while the loser drops to the semifinal Saturday evening to meet the winner the afternoon playoff.
South Korea qualified for the playoffs for the first time in its four appearances at the world championship.
The Americans won seven games in a row to get into a tiebreaker. So Pottinger's team has momentum and the Canadians need to generate some quickly Friday.
"Have you ever seen hungry Canadians? We're feisty," Nedohin declared. "We'll be back tomorrow.'
Canada led or co-led for all but one draw of the round robin. But their inconsistent performances in the home stretch contrasted starkly with two victories Wednesday when they looked comfortable and confident.
If the Canadians can't recapture that chemistry in time for the tiebreaker, the country will finish out of the medals for just the third time in the last decade.
"We're at least in the hunt," Nedohin said. "I think that's what I'm going to hold onto right now."
Nedohin, third Beth Iskiw, second Jessica Mair and lead Laine Peters were slow starters and strong finishers in the preliminary round, but their second-half surge went missing against the Scots and Italians.
"I would say the skip didn't show up today," Nedohin said. "I'll be there tomorrow.
"If anybody needs to play well, it's the person throwing the last shots and I take full responsibility of today. My performance was low and that's not what you get out of me. I'm surprised at two games back to back."
Canada squandered a chance to score two in the second end versus the Scots and they were not in the game after that.
Muirhead's team scored two in the third, stole two in the fourth and scored another three in the seventh.
Against Italy, Canada was in all kinds of trouble in the eighth end. Nedohin had to make a pressure draw just to limit the damage to a steal of one.
"We've had a season of great times, great moments and some flat days like that and we always bounce back really quickly," Iskiw said.
Canada opened the championship with an 8-7 win over Pottinger on Saturday. After losing four to open the tournament, Pottinger's St. Paul Curling Club rink went on an incredible run.
"A lot of games, a lot of rocks to get here," Pottinger said. "We're super-excited. Everyone's got a great feel for the ice, so hopefully momentum keeps carrying us right through."
South Korea made its world championship debut in 2005. Kim has skipped her country three of four times.
After going 3-8 in 2009 and 2-9 last year, she and her teammates took a monumental step forward in international women's curling.
"First time. Very exciting. Unbelievable," Kim said. "It's very difficult to make playoffs. Korea sees we are a team and now is very good."
Her curling team's performance here indicates the country is already ramping up for the 2018 Winter Olympics in Pyeongchang. But the 25-year-old Kim is plotting Olympic success before that.
"I want 2014," the petite skip declared. "I want to go to the Sochi Olympics."
Their coach Min Suk Choi says Kim is gaining confidence as she plays more international games. Kim's team also faced North American competition in World Curling Tour events in both Calgary and Medicine Hat, Alta., last October.
Sweden is a high-scoring team and led the field in ends scoring multiple points with last-rock advantage. Sigfriddson isn't afraid to give up two points to score three with hammer the next end.
"You have to give up two sometimes, especially at the worlds," Sigfriddson said. "The ice is really made for being easy to score two on, so you have to accept that. That's according to play sometimes."
Her lineup is unusual in that Sigfriddson throws lead stones, but holds the broom and calls the play in the house for her teammates. Maria Prytz throws fourth stones.
"It's what I like and that lineup is fast as well," Sigfriddson pointed out. "If I was second or third, we would play slower."
Sigfriddson defeated two-time Olympic and four-time world championship Anette Norberg to win the Swedish women's title and book their trip to the world championship. Sigfriddson downplayed the significance of it.
"I think that Anette is a little bit bigger all around the world and not in Sweden," Sigfriddson said. "Of course she's done a tremendous job for curling, but we've played her so many times and we know we can beat her."
Scotland posted a 6-5 record ahead of Germany's Melanie Robillard and Denmark's Lene Nielson at 5-6 and Russia's Anna Sidorova at 4-7. Italy and China's Bingyu Wang finished 3-8 and Linda Klimova of the Czech Republic at 2-9.