Semin was injured Saturday during the Hurricanes' 4-2 loss to the St. Louis Blues on a hit by Blues defenseman Alex Pietrangelo. Semin returned to the ice briefly after the hit, but left the game for good in the second period.
The 29-year-old was out of the lineup Monday against the Boston Bruins.
Semin, who was second on the Hurricanes with 44 points last season, has three goals and six assists in 20 games this season.
Just the feel for the direction they were headed and what they're trying to do, it just felt that this is a really good thing for this organization. They've got the pieces. We can put something together and go on a run or two and be together for a while, and I'm really excited about that opportunity. The team we have here has an opportunity to win, and that's the most attractive thing.
— Washington defenseman Matt Niskanen on why he decided to sign with the Capitals