The 35-year-old goalie did not dress in a 5-0 loss to the Chicago Blackhawks on Monday. He made 19 saves in a 5-2 win against the Columbus Blue Jackets on Saturday.
"They're telling me three weeks," Senators coach D.J. Smith said. "So, it is what it is. We'll keep grinding."
It's the second time this season Talbot will have missed games with a lower-body injury. He was injured against the New York Islanders on Jan. 25 and returned Feb. 24. He won three of four starts before sustaining his latest injury.
Talbot is 15-14-1 with a 2.85 goals-against average, .905 save percentage and one shutout in 32 games (29 starts) this season. He was acquired by the Senators from the Minnesota Wild in a trade for goalie Filip Gustavsson on July 12 and can become an unrestricted free agent at the end of the season.
Mads Sogaard started against Chicago and "will be the guy we run with here," Smith said.
The 22-year-old goalie is 5-1-1 with a 2.94 GAA and .899 save percentage in eight games (seven starts) this season.
"It [stinks] to hear what's happening with Cam," Sogaard said. "He's a huge part of this hockey team and a guy that I lean on a lot, for sure, for help and all that. To not have him is definitely a hit, for sure. I'm just going to do my best to help the team win and put them in a situation to win hockey games. That's all we can do, as goaltenders."
Kevin Mandolese was recalled from Belleville of the American Hockey League on an emergency basis Monday. He is 1-1-0 with a 2.45 GAA and .938 save percentage in two NHL starts.
The Senators (33-27-4) are four points behind the Pittsburgh Penguins for the second wild card into the Stanley Cup Playoffs from the Eastern Conference. Ottawa has not qualified for the playoffs since 2017, when it lost in seven games to the Penguins in the Eastern Conference Final.
Ottawa, which plays 15 games in March, won 5-4 at the Seattle Kraken on Thursday.
"It's our toughest month, we've talked about it," Smith said. "We're [3]-1 (so far). No game can be bigger than another one. At the time, they seem bigger, but you've got to be over .500 in March to give yourself a chance."
NHL.com independent correspondent Callum Fraser contributed to this report
