Bruins goaltender Tuukka Rask reacts after giving up the game-winning goal to Florida Panthers center Mike Hoffman in a shootout Tuesday night at TD Garden in Boston. The Panthers won 5-4. Charles Krupa/Associated Press

BOSTON — Considering the Boston Bruins’ blazing hot start, qualifiers and excuses were handy for the various stubbed toes they’ve suffered over the last week.

Allowing four straight goals to the Penguins? No worries, they pulled it out in the end. Losing to the Canadiens? Hey, things happen in Montreal, and don’t you know they got another goal called back. Dropping a game to the last-place Red Wings? Those things happen, and there’s no reason to fret over a road loss in November. The shootout loss to Philly? At least they showed some character to wipe out a two-goal deficit.

But Tuesday’s shootout loss to the Florida Panthers? There is no silk hat big enough to cover that pig of an outcome for the Bruins.

The Bruins entered the third period with a 4-0 lead. But for various reasons – bad defensive zone coverage, shaky goaltending, great scoring chances that went unfinished, a couple questionable penalties – the Garden crowd was sent home without “Dirty Water” in its collective head. They lost the lead, then the game, 5-4.

Maybe this is the game that finally turns it around for the Bruins, but Stanley Cup contenders do not often lose games like this.

Coach Bruce Cassidy held a no-nonsense practice on Monday, and he saw the exact defensive response to the previous subpar efforts he was looking for in the first two periods. Now he’s got to find another button to push.

“Yeah, you’ve got to be concerned,” said Cassidy. “It’s the strength of our team to close out games. I think we had a perfect record when we had a lead going into the third period. It’s a trademark of this team. So, yeah, it is a concern.”

Goalie Tuukka Rask, so good through the first month of the season, has now lost three straight, two of which he could take a big share of the blame. He admitted he was too deep in his net on Aaron Ekblad’s goal in the first minute of the third that gave the Panthers life, and then he appeared to be fooled on Mike Hoffman’s shovel shot that made it 4-3.

“I should have been sharper in that third period,” said Rask. “A couple of soft goals.”

To give the Bruins a little leeway, they are down a handful of wingers, with Providence call-up Zach Senyshyn (lower body) joining Jake DeBrusk, David Backes, Brett Ritchie and Karson Kuhlman on the shelf, along with defenseman Torey Krug.

But that’s not much of an excuse in this one. They should have been able to protect a four-goal lead with 20 minutes to go. And Keith Yandle’s tying goal with 1:39 left in regulation occurred with their top defense pair of Zdeno Chara and Charlie McAvoy and top line of Patrice Bergeron, Brad Marchand and David Pastrnak on the ice. Yandle was able to get to a loose puck in the slot and pop it over Rask.

Cassidy wasn’t wild about the penalty kill, which allowed two goals. He bemoaned the missed scoring chances. But watching his best players allow the equalizer might have bothered him the most.

“This is a team that has closed out games for years, and the last goal to me, putting everything else aside, is disappointing,” said Cassidy. “We get beat one-on-one off the rush, wingers circling out of the scoring area knowing that the game’s on the line. I could sit here and argue that a guy’s holding Bergy’s stick and he can’t clear the puck at the end. But structurally we were bad on that last goal. That’s the disappointing part to me. That’s where we’re usually rock solid.”

The Bruins had a CBA-mandated day off on Wednesday, then a practice day on Thursday before a very tough back-to-back. They face the Maple Leafs in Toronto on Friday, then come home to face the Washington Capitals, arguably the best team in the league, on Saturday. If they sweep those games, all of this will be forgotten. But right now it seems they’ve hit a mental wall that is preventing them from playing a full 60 minutes.

“It’s going to sting for a few days, but maybe it’ll be a good motivating factor going into Toronto and then playing Washington,” said Cassidy. We’ve got two strong teams coming up. Hopefully our guys have a little bit of burr in their saddle and want to get back in the win column.”

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