Boston Bruins goaltender Tuukka Rask (40), of Finland, turns the puck away as St. Louis Blues’ Alexander Steen (20) tries to score during the third period in Game 1 of the Stanley Cup Final on Monday, May 27, 2019, in Boston. Bruins’ Charlie McAvoy defends at right. (AP Photo/Charles Krupa)

BOSTON — Tuukka Rask first caught coach Bruce Cassidy’s attention as a hot-headed minor leaguer who was throwing milk crates onto the ice when things didn’t go his way.

These days, the Bruins goalie is much more likely to shrug off a mistake than break his stick over a crossbar.

“I just think he’s been real calm for a while now, on and off the ice, really even-keeled,” Cassidy said Tuesday, a day after Boston beat St. Louis 4-2 in Game 1 of the Stanley Cup Final. “He’s gotten upset … but he always gets it right back. That’s typically Tuukka.”

Boston Bruins goaltender Tuukka Rask, of Finland, stands in net during the third period in Game 1 of the Stanley Cup Final against the St. Louis Blues on Monday, May 27, 2019, in Boston. (AP Photo/Michael Dwyer)

The Bruins are three wins away from their second NHL title this decade, and Rask is a big reason why. After a so-so regular season that had backup Jaroslav Halak challenging for his job — and many fans calling for the team to make the change — the unflappable Finn has gotten better even when the strain of the playoffs seems to be wearing everyone else down.

He has given up three or more goals just three times this postseason, and he finished off the last two rounds with shutouts that have dropped his goals-against average to 1.85. He is well on his way to becoming the first goalie to win the Conn Smythe Trophy as playoff MVP since 2012.

For a different view of the goalie, Cassidy suggested viewing Rask’s viral hissy fit after losing a 2009 AHL game in a shootout on a goal that he thought hit the crossbar. Rask took his stick to the net like an axe, then flung it across the rink as he skated off; when he got to the tunnel, he found a milk crate that also found its way back to the ice.

Rask doesn’t do that anymore. He has matured and he also realized it was fruitless.

“It doesn’t do anything” to lose your temper, he said Tuesday, his arms crossed and his shoulders in what seemed like a permanent shrug.

Instead, he has been able to put mistakes or bad luck behind him, and Cassidy said that was the turning point after St. Louis opened a 2-0 lead in the opener.

“You want to have that to not let games get away from you,” the coach said. “There’s always, in games every night, where things can get away from you. Typically, you need your goalie to make the next save when it is 2-0.”

Rask did that.

And he also made every save after. (Though there weren’t that many: The Blues were outshot 18-3 in the second period, and 38-20 overall.)

“Everybody has to pull their load. That’s the only way you can win,” Rask said. “Individuals can have performances in certain games and turn the tide, but at the end of the day it’s a team sport and everybody needs to pull along and that’s why we’ve been successful.”

Although Rask won the 2014 Vezina Trophy and is the career leader in save percentage and goals-against average among active goalies, Bruins fans have resisted embracing him.

He was in net when the Bruins blew a 3-0 lead to the Philadelphia Flyers in the 2010 playoffs, and when the Bruins won it all the next season he was Tim Thomas’ backup. Thomas was gone and Rask was the starter two years later when they went back to the Cup final, but the Bruins lost to the Chicago Blackhawks after Rask allowed two goals in the last 76 seconds of the sixth and clinching game.

The next year, Rask was the league’s top goalie.

But the Bruins hadn’t been able to sniff much playoff success again until this year. Although the regular season was one of his worst — his goals-against average was 2.48, his second-highest as a regular — he played in only 46 games. He said the rest is paying off now.

“I think there’s a big difference when you play 45 or 65 games,” he said. “You don’t have that time to get the rest that you kind of want to.”

Rask’s name is already on the Stanley Cup with the 2011 team, and he said the accomplishment is not diminished by the fact that he didn’t appear in the postseason.

“Everybody in the room has a role,” he said. “I played a lot of games in the regular season and then didn’t play a second in the playoffs. But for us, it didn’t matter if you played or you didn’t play. If you’re a seventh (defenseman), eighth D-man, backup goalie, you were still doing something to contribute. It was great. You need that.”

That’s part of his message to his younger teammates who are in the final for the first time: Don’t waste the opportunity, and don’t forget to enjoy it.

And don’t let your emotions take over.

“On the ice, it’s a game and you just try to keep your nerves as calm as possible, I guess,” he said. “Experience helps on that.”

AP Hockey Writer Stephen Whyno also contributed to this story.