Stone, 24, sustained the concussion at training camp Friday.
A sixth-round pick (No. 178) by Ottawa in the 2010 NHL Draft, Stone was second on the Senators and first among forwards with 61 points (23 goals, 38 assists) last season. He had 26 goals and 38 assists in 80 games and finished second in Calder Trophy voting in 2014-15.
Forward Curtis Lazar, who is recovering from a case of mononucleosis, will be able to return to the ice soon, Boucher said.
"I'm feeling good," Lazar said. "It's a slow process. I know that I can't rush it by any means due to the spleen and the fatigue and all that. [I'll be] able to get in a preseason game or two, I think that's realistic. I got some good news from the doctors [Friday] that there has been improvement with my spleen and the swelling, so again, day at a time and keep rehabbing."
Lazar, 21, was selected with the No. 17 pick in the 2013 NHL Draft. He had six goals and 14 assists in 76 games last season.
