Eller was injured during the second period of Washington's 4-3 overtime loss in Game 2 on Monday. The best-of-7 series is tied 1-1. He took part in the morning skate Wednesday.
"Lars is an important player for us," Capitals coach Peter Laviolette said Tuesday. "He's done a really good job, he's handled big minutes against big opponents, and he's played well for us, especially in the last month."
Centering a line with Conor Sheary and Michael Raffl, Eller has been pivotal to the Capitals' defensive plan against the Bruins' top line of Brad Marchand, Patrice Bergeron and David Pastrnak. The Capitals held Marchand, Bergeron and Pastrnak without a point at even strength in the Capitals' 3-2 overtime win in Game 1.
But Bergeron and Marchand each scored a goal in Game 2, including Marchand's game-winner 39 seconds into overtime. Before Eller was injured, he assisted on Garnet Hathaway's goal that tied the score 2-2 with 3:18 remaining in the first period.
Eller scored 23 points (eight goals, 15 assists) in 44 games during the regular season, when he missed seven games from March 15-28 with a lower-body injury.
He also is one of the Capitals' most reliable centers on face-offs. Eller won a Capitals-high 48.6 percent of face-offs in the first two games of the series, while the Bruins have won 61.5 percent of the draws.
"It's always not easy when you lose your teammate," defenseman Dmitry Orlov said after Game 2. "Everybody steps up and tries to play some different lines and different roles, so it is what it is. It's not the first time this happened."
The Capitals began the playoffs shorthanded at center with Evgeny Kuznetsov not ready to play after exiting NHL COVID-19 protocol Sunday. Laviolette opted to shift T.J. Oshie from right wing to center.
Kuznetsov and goalie Ilya Samsonov, who exited COVID-19 protocol Saturday, have skated the past three days and traveled with the Capitals to Boston, but Laviolette wouldn't say if either will be available to play Wednesday.
"They're out there and that's a good sign," Laviolette said.
Kuznetsov, who usually centers one of the Capitals' top two lines, scored 29 points (nine goals, 20 assists) in 41 games during the regular season. He's scored 62 points (27 goals, 35 assists) in 78 games in the Stanley Cup Playoffs, including an NHL-leading 32 points (12 goals, 20 assists) in 24 games when Washington won the Stanley Cup in 2018.
Kuznetsov's return potentially would be a boost for the Capitals regardless of whether Eller is healthy enough to play.
"You guys have seen him at his best," Laviolette said. "He's an offensive talent. He's a guy who can make a difference in a game."
