The forwards were injured during a 5-2 loss to the Montreal Canadiens on Thursday. Duchene sustained a groin injury in the second period and is week to week; Ryan left in the first period with a concussion and there is no timetable for his return.
"When you lose high-end players, guys that are huge parts of your team, when you lose one it's big, when you lose two it's gigantic," Senators coach Guy Boucher said Saturday prior to a 2-1 overtime win against the Pittsburgh Penguins. "That's just the reality. You've got to figure out a way to have an identity, give yourself a chance to win ..."
Duchene was tied for ninth in the NHL with 34 points (12 goals, 22 assists), 13 behind leader Mikko Rantanen of the Colorado Avalanche.
Duchene played 82 games last season for Ottawa (68) and Colorado (14) and has missed 23 games since the 2012-13 season.
Ryan had 18 points (six goals, 12 assists) in 29 games this season.
"Anytime when you lose guys of that caliber, it's definitely going to hurt," goalie Craig Anderson said. "But again, you can't look at it as 'Woe is me.' You've got to look at it as an opportunity for another guy to step in, fill that role, maybe pick up some of those points that those guys are leaving on the table."
The Senators on Friday recalled forward Nick Paul from Belleville of the American Hockey League. He had one assist in six games for Ottawa this season.
NHL.com correspondent Callum Fraser contributed to this report
