Victor Hedman is day to day for the Tampa Bay Lightning because of an upper-body injury.
The defenseman didn't play after the first period in a 6-3 loss to the Washington Capitals on Saturday.
Hedman, who has 54 points (12 goals, 42 assists) in 70 games, likely will not play on Tampa Bay's upcoming four-game road trip, which concludes their regular-season schedule.
"Victor's doubtful for the rest of the trip, and that's basically all I can elaborate on," coach Jon Cooper said Monday before the Lightning defeated the Ottawa Senators 5-2 to start the trip.
Hedman won the Norris Trophy last season as the best defenseman in the NHL. He is tied for eighth among NHL defensemen with 42 assists this season and is 10th in points. He is averaging 22:46 of ice time per game.
Video: BOS@TBL: Hedman tucks in carom off end boards
"What changes is you can't take so many things for granted because he can make up for a ton of mistakes that happen," Cooper said. "He runs our power play unit, he's a driving force in our 5-on-5 play, and he plays on the penalty kill, so it's one of those things that you can throw every cliche in the book of 'next guy up' or 'spread the minutes around,' but it's a big loss for us. As I said, it's all about getting to the playoffs at this point and making sure we stay healthy, and if we can make sure [Hedman] is at that point, we'll be OK"
Lightning defenseman Anton Stralman, who has missed 10 games with a lower-body injury, participated in the morning skate Monday. Defenseman Dan Girardi remains out with a lower-body injury that has sidelined him 10 games.
"Hopefully, we'll have a Girardi sighting at some point," Cooper said. "Our goal is to have everybody back by whatever day Game 1 [of the Eastern Conference First Round] is. And we're taking the steps to make sure that happens."
Lightning goalie Louis Domingue is day to day because of a lower-body injury. Tampa Bay recalled goalie Edward Pasquale from Syracuse of the American Hockey League on Monday.
Domingue, who last played March 21, is 21-5-0 with a 2.88 goals-against average and .908 save percentage in 26 games.
Pasquale has played one game this season, making 19 saves in a 6-5 shootout win against the Detroit Red Wings on Dec. 4.
The Lightning (60-15-4) became the third team in NHL history with 60 wins in a season, joining the 1995-96 Detroit Red Wings (62 wins) and the 1976-77 Montreal Canadiens (60).
NHL.com correspondent Callum Fraser contributed to this report