The deal has an average annual value of $3.5 million.
Eller, 28, has registered 28 points (11 goals, 17 assists) in 53 games this season, which ranks sixth on the Capitals. He is three points shy of a personal single-season high, set in the 2012-13 season with the Montreal Canadiens.
The Capitals acquired Eller from Montreal on June 24, 2016. The Rodovre, Denmark, native owns 53 points (23 goals, 30 assists) in 133 games with Washington.
--The Vegas Golden Knights placed backup goalie Malcolm Subban on injured reserve with an upper-body injury suffered during Thursday's morning skate. There is no timetable for the 24-year-old's return.
With Subban out, the Golden Knights recalled netminder Maxime Lagace from the Chicago Wolves of the American Hockey League. Lagace is expected to be available for Vegas' game against the Philadelphia Flyers on Sunday.
Subban has been a pleasant surprise for Vegas this season, posting an 11-3-1 record to go with a 2.59 goals-against average and .912 save percentage. The former first-round pick was claimed off waivers from the Boston Bruins in October.
--San Jose Sharks forward Joel Ward is out indefinitely with a right shoulder injury suffered in the team's 5-3 loss to the Golden Knights on Thursday.
Ward had rotator cuff surgery on the same shoulder during the offseason. He said Saturday that he will have X-rays and an MRI once the swelling in the area subsides and that he remains optimistic he will return this season.
"I took a good little pop there. Right now it's just kind of re-evaluating," Ward said. "It's kind of day to day. At first I was a little worried for sure, but kind of woke up a lot better. Just basically come in here and get some treatment done again and hopefully kind of get back in, hopefully soon, but I don't know when. ... No surgery needed, which is good. I was thankful for that."
--Field Level Media