A win over a fragile St. Louis Blues team may not be a big deal for a team with high expectations.

But for where the Bruins are right now, the manner in which they won on Tuesday in St. Louis could be a good start for them to get to where they want to go.

After spotting the Blues and their 32nd-ranked power play a 2-0 lead, the B’s stormed back with three third-period goals to notch a 3-2 victory, their most emotional win of the season.

There was plenty of desperation in evidence in the comeback win, with David Pastrnak’s first goal in eight games the game-winner with the less than two minutes left.

“(There was) belief in the room. We could feel it,” said Pastrnak, who had 10 shots on net in 24:29 of ice time. “Obviously we didn’t have any goals going into the third but there was something different. We felt like we were going to get it. It was a just a matter of time. Obviously, heck of comeback for us and big win for our group.”

Down 2-0, the Bruins got one back at 4:53 of the third from Morgan Geekie, back in the lineup after three straight healthy scratches. Pastrnak stole the puck from Colton Parayko in the neutral and took off with Geekie on an odd-man rush. Geekie took Pastrnak’s pass and beat Jordan Binnington to the blocker side for his first of the year.

The B’s then tied it at 9:15. Brad Marchand settled a loose puck and fed Charlie McAvoy up top. McAvoy’s hesitancy to shoot got him bounced from the first power-play unit but, on this play, he let a one-timer rip from the high slot to beat Binnington.

And finally, with 1:47 left in regulation after a mad scramble for the puck in the offensive zone, McAvoy made a great dish over to Pastrnak, whose blast broke through Binnington for the go-ahead goal.

It was the B’s first comeback win of the year.

“Mac and Pasta, I think they weren’t going to let us lose tonight,” coach Jim Montgomery told NESN. “You could just see it, that they were stepping out on the ice with an elevated purpose in the third period. And Morgan Geekie, really proud of him. He sat out three games in a row, but I could see his work ethic in practice coming and coming. That’s his best game of the year. That’s the Morgan Geekie we know can help the Bruins every night.”

One of the more intriguing pregame stories was the change of the first power-play unit with Hampus Lindholm replacing McAvoy up top.

And it didn’t take long before the PP got its chance. In fact, they got two advantages in the first 8:23. But as far as results went, it was the same ol’, same ol’. They got some shots on Binnington, but none that were really high-percentage ones and the movement on the PP never really had Binnington moving much in his crease.

Pastrnak said on Monday that he needed to shoot more and he took his own advice. He had six of the B’s nine shots in the first period.

The Blues’ struggling PP had one chance that the B’s killed, thanks in part to a big block by the defenseman Lindholm that caused him to leave the game. It appeared he took the shot on the inside of the right knee.

The Blues’ best chance came earlier in the period. Jordan Kyrou had a clean breakaway from the offensive blue line but Jeremy Swayman was able to steer his backhand attempt wide.

The B’s got a third power-play chance 1:02 into the second period and, with Hampus Lindolm unavailable, McAvoy went back with the top unit. The B’s did every thing but score. They got four shots on net, which did not include their best chance on a pretty tic-tac-toe play. Elias Lindholm fed Brad Marchand on the left side and Marchand, selling a shot to freeze Binnington, fed Pavel Zacha for what looked like a tap-in. But Pastrnak also got his stick in there and the puck went wide.

And when Cole Koepke took an offensive zone high-sticking penalty, you know what was coming next. On the PP, Swayman stopped Kyrou’s shot from the bumper, but Brayden Schenn was there to clean up the rebound for the 1-0 lead at 9:24. It was the Blues’ first power-play goal on home ice all season.

They would soon get their second as the B’s weren’t done shooting themselves in the foot.

Pastrnak then took another offensive zone high-sticking and, at 12:12, the Blues had a 2-0 lead when Oskar Sundqvist scored an easy backdoor goal.

Any wind the B’s may have had in their sails was gone. When they got another power play Radek Faksa high-sticked Tyler Johnson, there was little urgency and it went by the boards without much of a danger of scoring.

The B’s were down just two goals going into the third period. In the last couple of years, that would have been challenge, but a surmountable one. With this team, it seemed like Mt. Everest. But they managed to scale it.