General manager Bryan Murray said Thursday that Stone suffered a microfracture of his right wrist and some ligament damage from a slash by the Montreal Canadiens' P.K. Subban in the series opener.
There was no official word from the NHL on whether Subban will be suspended, but some reports said the league decided no further discipline was needed. He was given a major penalty and a game misconduct for the slash at 8:23 of the second period of Montreal's 4-3 victory.
The incident may ramp up emotion for Game 2 of the best-of-seven series on Friday night at the Bell Centre.
Murray said a suspension was warrented because of the injury. He also suggested it was a premeditated attack on Ottawa's hottest scorer, which Subban denied.
"The disturbing part from our point of view is that there was a threat made before by Subban to Stone," said Murray. "There were two attempts on faceoffs to slash him, one connected.
"Then he two-handed him across the wrist in front of the net. (Stone) has been, if not the top, one of the top five players in the league the last two months of the year. It's huge loss."
He said the league should investigate whether Subban threatened Stone.
Subban felt the officials made the right call, but added: "I've never threatened anybody out there.
"I don't think I would. I'm not really the toughest guy out there without my gloves on. I'm not really going out there looking for fights like that."
Stone was skating near the Montreal net during a second period power play when Subban gave him a two-handed chop on the wrist. Stone went down in pain, then rushed off the ice. He came back later in the period, left again, then returned during the third.
It may have influenced the league that Stone was able to return, but Murray said the player was being "courageous" in trying to come back and the true nature of the injury wasn't known until after the game.
The extent of Stone's injury was unclear. Asked if he was ruled out for Game 2 on Friday night, Murray said: "I would assume. I think the trainers have worked on him and Mark is willing to take shots or whatever it is, but he has no mobility at this point at all."
In his postgame comments, coach Dave Cameron appeared to threaten Montreal when he said that either Subben be suspended or the Senators might slash a top player and take a major penalty themselves.
Both Cameron and Murray backed off that stance, saying that maintaining discipline was key.
"It's very important that we don't (retaliate)," said Cameron. "One of our keys is discipline over emotion. The best way to get even is win the hockey game."
If Stone can't play, Cameron will also have to adjust his lines. In practice, Milan Michalek moved into Stone's spot on right wing with Kyle Turris and Mike Hoffman. Alex Chiasson moved onto the second unit with Mika Zibanejad and Bobby Ryan.
More ominously, tough guy Chris Neil, a healthy scratch for the opener, skated on the fourth line.
Asked if he'll target Subban, Neil said: "I think they get last change. I probably won't get up against him."
Stone was on fire as Ottawa went 22-4-4 down the stretch to clinch a playoff spot on the final weekend of the regular season. He put up 35 points in the final 31 games and was on a nine-game points streak heading into the post-season.
"He's a great hockey player," said Turris. "He's been a huge part of the run we've been on.
"But we'll move forward as if he's not returning and, if he does, it's a bonus."
Al sides agreed the referees made the right call.
The major and game misconduct fell under rule 61.4 of the NHL rulebook dealing with match penalties. It says, "The referee, at his discretion, may assess a match penalty if, in his judgment, the player attempted to or deliberately injured his opponent by slashing."