Playing without second Jessica Mair because of a stomach ailment, Canada lost 8-4 to Sweden after an earlier 7-5 win over Russia on Tuesday.
Canada was in a three-way tie for second at 5-2 behind leader Ji-Sun Kim of South Korea at 6-1. Sweden's Margaretha Sigfriddson and Switzerland's Mirjam Ott were also 5-2.
Mair took herself out of the Monday's night's game after the sixth end, pressing alternate Amy Nixon into service for the remainder and both games Tuesday.
"She hasn't thrown up since one o'clock in the morning," was Nedohin's status report on Mair. "So that's a good sign. We've been avoiding her. She's in her own room. Crossing my fingers, (she'll be in) the morning game. I hope she has a good night."
A vicious stomach bug knocked several players out of multiple games at the Canadian women's championship last month in Red Deer, Alta., although Nedohin's team dodged it.
Canada and South Korea meet Wednesday morning in what is now an important game for the hosts.
"I think it will be very difficult," Kim said. "That's OK, no problem. Not scared. (We're) ready."
After winning just two games at last year's world championship, Kim is the surprise of this year's tournament. It signals her country has already begun ramping up sport preparation to host the 2018 Winter Olympics in Pyeongchang.
Kim stole points beat China 7-5 and Denmark 7-6 on Tuesday.
Allison Pottinger of the U.S., Denmark's Lene Nielson, Scotland's Eve Muirhead, Germany's Melanie Robillard and Russia's Anna Sidorova were all 3-4. Italy's Diana Gaspari, Linda Klimova of the Czech Republic and China's Bingyu Wang were 2-5.
The top four teams advance to playoffs at the conclusion of the round robin Thursday.
Sigfriddson defeated two-time Olympic champion Anette Norberg at Swedish nationals for the right to play in this world championship.
Her Skelleftea foursome plays an aggressive game to score points in bunches. In an unusual permutation, Sigfriddson throws lead stones, but runs the house.
Maria Prytz throws fourth stones and did not miss against Canada with a shooting percentage of 95 per cent to Nedohin's 87.
"She has the nerve and the eagerness to play last rock,"Sigfriddson said of her fourth.
Nedohin and Sigfriddson went hard at each other early, forcing the other team to come through tight ports for draws and takeouts, as well as make precise runbacks.
The Enmax Centre was not full, but the crowd that was there was loud and the arena's tight confines gave the night draw a raucous feel.
The Swedes scored three in the third on the strength of angle hits by Prytz. They won the runback battle in the fifth end to score another three and lead 6-3 at the halfway mark. They stole a point in the eighth when Nedohin's shooter rolled wide on a hit.
"We were tucking around things (but) showing little slivers and they played really well," Nedohin said. "We're going to lose some games, but they played well.
"We need to play better. There's no doubt. Definitely we can perform better. We know that."
Nixon curled 78 per cent against Russia and 85 per cent against the Swedes in Mair's absence.
"I'm hoping Jessica can come back because it's a lot easier with your core team members, but I'm ready to go if necessary," Nixon said.
Curling teams routinely book a hotel room that can serve as a quarantine room. Nixon moved in with lead Laine Peters so Mair can have her own quarters.
Dealing with illness on the team is easier when the world championship is in Canada because of familiarity with the medical system, Nedohin said. But it's also stressful for a player to take herself out of the game.
"It's really crummy as a player," Nedohin said. "You could see it in her eyes last night. She was crying. We all want to be here. It's hard not to have Jess, but it's not a big deal.
"It's Tuesday and we'll have her back by the playoffs."
The success of Nedohin's team is partly due to their on-ice chemistry. Nedohin and vice Beth Iskiw banter at the back of the house, while lead Peters and Mair often break into giggles while they're sweeping.
A lineup change has the potential to be disruptive, but Peters and Nixon, the two Calgary-based players on the team, play in a league together.
"We're buddies," Nixon said. "We play on a Wednesday-night league team. We were out there today and I said 'It's exactly like league.'"
Nixon brings the experience of playing in an Olympic Games. She was third for Shannon Kleibrink's team that won bronze in 2006 in Turin, Italy.
She knows what it's like to be sick at a major championship. Nixon had a similar bug while playing in the semifinal and bronze-medal games at the Olympics.
"I can exactly imagine how Jess feels. It's so stressful and frustrating and heart-wrenching," Nixon said. "You want to come in when you can, but you're not exactly sure how you're going to feel when you get sweeping. It's a hard call to make."
Nixon recently parted company with Kleibrink after nine years to skip her own team. Kleibrink's not the only elite women's team to make changes. Amber Holland, last year's Canadian champion, said earlier this week she's disbanding her Kronau, Sask., foursome.
"What Amber Holland said yesterday kind of resonated with me, which is every team has its time,'' Nixon said.
"We had a good run. It's a great team with great players. I think they'll be wildly successful without me. I thought it was time to do something different."