Not only that, they couldn't hold a 3-0 lead in Friday's night's Game 7. Philadelphia dug out of the early hole, tied the game midway through the second period and won 4-3 on Simon Gagne's goal with 7:08 remaining -- on a power play triggered by a bench minor for too many men on the ice.
Instead of preparing for a Sunday night date with Montreal, the Bruins will spend Saturday packing their gear for a summer vacation that's starting too soon -- while joining the 1942 Detroit Red Wings and the 1975 Pittsburgh Penguins as the only teams in NHL history to lose a playoff series after winning the first three games.
To say it was a crushing loss would be an understatement.
"I've had some Game 7s losing in the semifinals, but this one hurts," admitted 42-year-old forward Mark Recchi, one of Boston's best players in the playoffs. "You don't get too many chances to get to the third round."
As to what happened, Recchi was succinct.
"The killer instinct was missing," the two-time Stanley Cup winner said. "What are you going to do? It's over and we've got a long summer to think about it. It's disappointing."
Especially because of the way the game started.
The Bruins came out flying, scoring three times in the first 14:10 to take a seemingly insurmountable 3-0 lead. Michael Ryder scored once and Milan Lucic twice -- and the only question appeared to be how many goals the Bruins might score against Michael Leighton.
However, someone forgot to tell the Flyers that the game was over -- they got a goal by rookie James van Riemsdyk late in the opening period and stormed the Boston zone in the second, tying the game before the period was halfway gone on goals by Scott Hartnell and Danny Briere.
"We rose to the occasion to start the game. We were physical and aggressive to start the game," Lucic said. "And just because we were up 3-0 doesn't mean the game was over. They came at us and were relentless and did what they had to do to win the game and the series."
Both teams hit a post in the third period before the decisive penalty occurred with 8:50 left and the Bruins on a line change.
"I saw two centermen out there and I said, 'What's going on,'" Lucic said. "I knew there was a miscommunication out there and we got caught.
"At that point of the game, you can't be taking a penalty like that. They got a late goal, it wasn't mean to be for us, and you've got to live with it."
Gagne scored with 18 seconds remaining in the power play.
Many of the 17,565 fans at TD Garden showered the ice with mini-towels as the game ended.
Boston coach Claude Julien offered no excuses for his team's failure to capitalize on one final chance to close out the series.
"The bottom line is, we had a 3-0 lead in the series. We had a 3-0 lead tonight. We blew both," he said. "There's no excuses. We have to take the responsibility that goes with it. Everyone. We had four tries at it and we weren't able to do it."