Patrice Bergeron, who was making his series debut, said the Bruins as a whole must accept responsibility for the loss.
"He's been a rock for us all year," Bergeron said of Ullmark. "He's given us a chance to win every time he's stepped out there. He can't be too hard on himself. We're a team, it's about what we do together on the ice as a unit of six and go from there. To me, I feel you win and you lose as a team. It is what it is.
"He's a tremendous goalie, he's probably the best goalie in the NHL and probably going to win the Vezina this year. We're all there for each other and we've always said that, so chins up for him."
The game was inches away from ending before overtime when Brad Marchand nearly sealed the series at the buzzer when he broke in all alone on a breakaway with just four seconds to go in regulation. Marchand fired a wrister at Sergei Bobrovsky with about a second left but the Florida netminder denied the chance to send things to extra time.
"Yeah, it was tough," said Marchand. "I was racing against the clock. I was trying to count down, I kind of glanced up to see how much time was left and I was trying to get as close as I could with where I thought the time was. Had to rush the shot but wouldn't mind having that one back."
The chance came moments after the Bruins had another opportunity to close out the Panthers, who were assessed a minor penalty for too many men on the ice with 3:35 to go in the third period. Boston, however, failed to convert after having potted two power-play goals earlier in the contest (Marchand at 2:27 of the second and Bergeron at 4:33 of the third).
"I thought our power play could have sealed the game there, the last power play, but I don't even know if we got a good look on it, to be honest," said Montgomery. "But we got two power play goals in the game, so we've got to get more five-on-five scoring when we're at home. We got a lot in Florida, but we didn't get enough in the three games at home so far."
Overall, the Bruins - who were 34-4-3 on home ice this season - have now dropped two consecutive games at TD Garden, while struggling to find much traction in any of the three contests on Causeway Street during this opening-round series.
"Well, in Boston there has been, that's for sure," Montgomery said when asked about the B's lack of concentration. "For whatever reason, we didn't start on time…we tend to make big mistakes right now, I don't know why, the last two games at home. We don't manage our ice or manage the puck, it's one of the two…when you're chasing the game like we did all night, 1-0, 1-1, 2-1, 2-2, 3-2, 3-3, and then obviously you can't chase the game anymore, you spend a lot of energy.
"I thought the energy that we spent in the second and the third trying to tie the game up … I didn't think we were as sharp in overtime."