The hockey goalkeeper participated in the informal training on Monday, together with, among others, Bäckström and Carl Hagelin.
He wore his new mask with pictures of the Capitol, the Washington Monument, the Lincoln Monument and the United States National Bird, the bald eagle.
Capitals posted a picture of Lundqvist on Twitter with the text "everyone's eyes are on the new guy".
Lundqvist will be an important cog in Washington.
- His presence and winning skull will spread to others, the rest of us, says Bäckström to Expressen.
The 38-year-old star goalkeeper left the New York Rangers after 15 seasons as a free agent and has signed for a season with Washington.
The veteran is expected to share the cage guard with 23-year-old Ilya Samsonov, for whom he will also be a mentor.
It has not yet been decided, but the NHL aims to start the season on January 1.
It is also not decided when the training camps will start.
- Right now I actually have no idea when it will be.
The only thing I know is that the players who are in Europe must return and be quarantined before they can start training with their teams, says Bäckström.