With Boston goalie Tuukka Rask out sick for the Bruins' last-gasp run at a playoff berth, backup Jonas Gustavsson allowed four goals in the first half of the second period and the Ottawa Senators went on to win the regular-season finale 6-1 on Saturday.
The Bruins can still make the playoffs if the Philadelphia Flyers get no more than one point in their last two games, including one later Saturday against Pittsburgh.
Chris Neil, Zack Smith, Matt Puempel and Mika Zibanejad scored over 8:18 in the second period, and Andrew Hammond stopped 39 shots for the Senators. Ottawa also had a pair of empty-net goals in the third when the Bruins pulled the goalie to create a two-man advantage on the power play.
David Pastrnak scored for Boston, and Gustavsson stopped 30 shots.