Sens head coach D.J. Smith confirmed the status of the veteran forward Sunday, a day after Ottawa's preseason concluded.
"It's his physicality, being in the league and his leadership but it's his energy day-to-day on the bench, holding guys accountable that is the stuff you don't see from up top," Smith said. "How much the guys respect him, how hard he plays, that's where we're going to miss him.
"He's willing to do anything for the team."
Watson played 34 games last year, scoring three goals and adding seven assists, but saw his season end on March 22 after suffering a hand injury blocking a shot.
In four preseason games, Watson had one goal.
"Watty brings a lot more to the team than the naked eye," Connor Brown said. "He's such a heart and soul guy and his willingness to block shots with any part of his body.
"His commitment to doing anything it takes to win is contagious so we'll miss him and hope he gets back soon."
