With their captain having left early for Sochi, the Boston Bruins suffered just their third loss in three weeks.
Chara left for Russia after a 3-1 home win over Vancouver on Tuesday because he's serving as Slovakia's flag bearer for the opening ceremonies. With their top defenseman gone, the Bruins (36-16-4) fell short of a third straight win Thursday despite coming back from a two-goal deficit in St. Louis.
"To me, I'm proud of the way we played, like the whole team, from the first line to the fourth line, all of our Ds were really good," coach Claude Julien told the team's official website. "... Unfortunate bounce to lose that game in overtime but still, again, a great effort from our team."
Boston fell to 4-5-4, including playoffs, without Chara since he left Ottawa to join the Bruins in 2006.
"I thought that we played pretty well throughout the game, especially with Zee out," defenseman Johnny Boychuk said. "The young guys stepped up and played extremely well the whole game. The score didn't really tell the tale, I thought we should have won, but sometimes you get the bounces.
"But the D played extremely well for having our team leader gone."
The Bruins are 7-1-2 since Jan. 15, winning four of five at home. They're 7-2-0 in their last nine visits from the Senators (26-21-11).
Boston blew out Ottawa 5-0 at TD Garden on Dec. 27, but the Senators followed with a 4-3 home victory over the Bruins the next night as an injured Chara sat out. The Senators won the previous two meetings by 4-2 scores, April 28 in Boston and Nov. 15 in Ottawa.
While the Bruins lead the Atlantic Division, the Senators are in sixth place but have gone 4-1-1 in their last six to climb to 10th in the Eastern Conference.
"It's going to be a really tough game in Boston," Ottawa winger Milan Michalek said. "We've got to be ready for that and try to get the two points."
His team avoided going winless on a three-game road trip with a 5-4 shootout victory over St. Louis on Tuesday, then beat Buffalo 3-2 on Thursday on Michalek's second goal of the game with 23 seconds left.
Michalek had broken a Senators record for fastest goal from the start of a period by scoring 10 seconds into the third. He has three goals in the past two games after scoring seven in his first 56, but he has none in his last 16 games against the Bruins.
Bobby Ryan has two of Ottawa's eight goals in the season series but has scored just two of his team-best 20 since the win over Boston on Dec. 28.
Along with Chara, Boston will also likely be without another defenseman, Adam McQuaid. He has missed the past eight games due to an injured leg and is not expected to return until after the break.