Torey Krug reflects on his huge hit against Robert Thomas in the third period of Game 1, saying he was trying to change the momentum on the play. (0:47)

BOSTON -- Boston Bruins veterans know that the Stanley Cup Final will be a physical series, and perhaps nobody set the tone better in Game 1 than 5-foot-9 defenseman Torey Krug.

After tangling with St. Louis Blues forward David Perron by his own net in the third period, Krug lost his helmet and -- in a highlight of the Bruins' 4-2 win over the Blues on Monday night -- skated the length of the ice with his hair flowing. Krug then delivered a huge hit on Blues rookie Robert Thomas. The defenseman soared in the air on his way down, momentarily evoking the iconic image of Bruins legend Bobby Orr, though in a much different context.

"Well, he got a haircut a couple days ago," teammate David Pastrnak said. "So he was looking pretty good."

After the game, Krug said Perron "ripped [the helmet] off my head."

The 28-year-old said he did not hit his head against the ice when he came down from the Thomas hit.

"No, all good," Krug said with a smile.

"Obviously, first and foremost, you want to take care of your head and make sure that you don't put yourself in a vulnerable position," Krug said. "I'm sure my coach and my GM were hoping that I would just get off the ice at that point. But that's hockey. That's all I can really say about that."

Krug later said his wife was probably concerned, which is not ideal considering she is pregnant.

The Bruins looked a bit rusty after a 10-day layoff between games and fell behind 2-0. But by the time of Krug's hit, the Bruins were buzzing thanks to an imposing second period in which they dominated possession and had 29 scoring chances compared to St. Louis' seven.

The Krug hit, however, seemed to put the Bruins in cruise control and rallied the bench. Asked what Krug's hit showed him, Bruins rookie Connor Clifton said: "His courage, and you don't want to mess with that guy. Don't make that guy mad."

Krug, who played collegiately at Michigan State but went undrafted, said he feels he has been targeted his entire career because of his size. Since Krug debuted in 2011, the NHL has begun favoring speed and skill -- meaning height isn't as important, and there are now more players of Krug's stature.

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It wasn't always that way.

"Every game in the NHL, since I've been in the league, [players have tried to get under my skin]," Krug said. "I'm a 5-foot-9 defenseman. I'd probably do the same thing if I was on the opposing teams. I'd probably try to run me straight through the boards. It's no secret a strength of mine is breaking out of the box. Their strength is beating on the forecheck. So they're going to be coming, I know that. They've been coming all playoffs. I welcome the challenge."

Krug and Perron tussled in wrestling-style moves for several seconds in front of Boston's net as an official looked on. Perron explained the scuffle from his point of view.

"I saw the puck going to the point," the Blues forward said. "I was just trying to get body position. You see some shoving. I'm just trying to make as much room for myself but also trying to generate some momentum for my club. Maybe he hit you one time too many and goes to the box. Knowing what the penalties are at, it was close to happening."

After being the most disciplined team through the first three rounds, the Blues took five penalties in Game 1. Game 2 is Wednesday in Boston.