Boston’s Marcus Johansson, left, celebrates with Charlie McAvoy after McAvoy scored goal against the St. Louis Blues during the second period in Game 1 of the Stanley Cup Final on Monday, May 27, 2019, in Boston. (AP Photo/Michael Dwyer)

BOSTON — Marcus Johansson was watching from afar a year ago, admittedly conflicted and a little “bitter.”

He was happy for his friends and former teammates as the Washington Capitals won the Stanley Cup and then raucously celebrated, just as Johansson had once dreamed of doing with them. But after he spent the first seven seasons of his career in Washington, he was traded to the New Jersey Devils the summer before the Capitals won a franchise-first championship.

“I talked to a couple of guys, but you kind of want to leave them to their celebrating, too,” Johansson said. “It looked like they had fun. I mean, who wouldn’t?”

Now it could be Johansson’s turn for Stanley Cup glory.

Acquired by the Boston Bruins in late February as a trade-deadline rental, the 28-year-old has three goals and six assists in 17 playoff games, part of a fast and skilled third line with center Charlie Coyle and right wing Danton Heinen. And after his career was temporarily derailed by devastating injuries, Johansson has rediscovered the game he so consistently flashed in Washington, even taking his new team by surprise.

“We knew he was a talented player,” Bruins coach Bruce Cassidy said. “I didn’t know he had that first step to separate. He’s a good passer. He’s actually got a great shot. We encourage him to use it more — he always looks pass first. In traffic, he’s grabbed some pucks and got in and out of traffic and been able to get in on the attack maybe better than I would’ve thought.”

Johansson was coming off a career-best 58-point campaign the summer the Capitals traded him for second- and third-round picks, and he acknowledged it blindsided him.

With hefty contracts awarded to forwards Evgeny Kuznetsov and T.J. Oshie, Washington needed to clear salary cap room, and Johansson was the casualty. He’d been largely healthy throughout his career, posting four straight seasons with at least 74 games played, but he suffered two concussions during that first year with the Devils, the second one sidelining him for more than two months.

He was back on injured reserve with an undisclosed upper-body injury in December, but he got hot just before the trade deadline with six goals and six assists in the 13 games before he was dealt to the Bruins. Then, in just his fourth game with Boston, Johansson was checked into the boards and suffered a lung contusion, another bad break after a string of them. That cost him three weeks, but he’s been healthy since.

“It’s never fun with injuries and stuff, but it’s part of the game,” Johansson said. “I’m not the first guy who’s had some issues. That’s just the way it goes. Knock on wood, I’m happy to be healthy right now, and it’s fun to be out there. . . . It definitely felt like I got back to myself a little bit, and it’s been going in the right direction.”

Johansson was arguably the most noticeable forward on the ice in Monday’s Game 1 with his eye-popping speed up the middle, a trademark of the Capitals’ power-play zone entries during his time in Washington. But he finished Game 2 with a minus-two rating and was on the ice for the St. Louis Blues’ game-winning goal in overtime.

The Bruins’ star-studded top line of center Patrice Bergeron and wingers Brad Marchand and David Pastrnak has been held off the score sheet (beyond an empty-net goal for Marchand) to start this series, which is tied at one game apiece, making Boston’s bottom-six depth that much more important.

“He can thread the needle, he can find you wherever, and he’s pretty crafty with it,” Coyle said of Johansson. “He’s been really good for us.”

“He backs people off because of his speed, and he’s made good plays to the second wave,” Cassidy said. “He’s attacked the net more since he’s been here. He’s driving wide, taking it inside, willing to go to the net when the opportunity dictates — a little greasier game, and I think that’s been the difference from maybe what we saw when he first got here.”

Johansson will be an unrestricted free agent this summer, able to choose his own destination for the first time in his career, and his impressive postseason play is expected to make him an attractive option for teams. But first he’s relishing reaching the stage everyone, including the Capitals, is still watching in June.

“You always envision that,” Johansson said. “It’s why you play. You want to be in this position to have a chance to win. Obviously, I didn’t know it was going to be here, but I couldn’t be with a better group, couldn’t be with a better team.”