MONTREAL -- Brady and Matthew Tkachuk came out hitting, started scoring and put together a display of brotherly dominance playing together for the first time on a big stage.

The Tkachuks each scored twice, flourishing after being put on the ice at the same time, as the United States beat Finland 6-1 on Thursday night in each team's opening game at the 4 Nations Face-Off, a physical showdown played with edge throughout.

"That's the way we play, one of the reasons why we're on the team," said Matthew Tkachuk, a reigning Stanley Cup champion who finished with three points. "You don't change your game. You play your identity. It's up to us and the rest of the guys to play to your strengths. That's one of them."

Everyone was finishing checks, including Jack Eichel dumping Finnish captain Aleksander Barkov into the U.S. bench. Brady Tkachuk bowled over 6-foot-6 Niko Mikkola with one of his game-high eight hits, and Matthew Tkachuk gave Patrik Laine an earful before a faceoff as the Americans began to take over.

Matthew called Brady "a beast," and coach Mike Sullivan said the brothers "just have a funny way of dragging us into the fight."

"We kind of knew what to expect after watching [the Canada-Sweden] game that it was going to be fast and physical," said defenseman Zach Werenski, who had three assists. "We have some guys on this team that can do that, right? You have the Tkachuks. We got [J.T.] Miller. We got a lot of big bodies. Eichel was throwing his body around tonight. I thought the pace was really good. I thought the physicality was good, and I thought we responded well to all of it."

The scoreboard made it look like more of a rout than it was for the first two periods, when quality chances were at a premium and space on the ice was hard to find. Matt Boldy scored the go-ahead goal on a textbook deflection of Minnesota Wild teammate Brock Faber's shot late in the second, then the floodgates opened early in the third.

Many fans hadn't even returned to their seats from intermission when Matthew Tkachuk sailed a long shot in past Juuse Saros 15 seconds into the period. Saros gave up another softie to Jake Guentzel 11 seconds later, and Brady Tkachuk beat the struggling Nashville goaltender again to make it three U.S. goals in three minutes.

"The start of the third, it was -- I don't know how to say that, but we weren't ready for that," said Finland coach Antti Pennanen, who acknowledged he and his staff considered pulling Saros.

That onslaught quieted the very pro-Finland crowd full of Canadians eager to root against their country's biggest hockey rival. Some even booed the U.S. anthem before the game, and there was plenty more where that came from for Toronto Maple Leafs captain Auston Matthews several times he touched the puck.

Matthew Tkachuk added another goal for good measure on the power play with 8:47 left, and that was enough for the "U-S-A!" chants to fill the bowl at Bell Centre. In the waning minutes, a few U.S. fans proclaimed, "We want Canada!"

They face off Saturday night.

"I think it's going to be the biggest game that I've ever played in my career," Brady Tkachuk said. "We've been talking about that game especially. Really excited to experience it."

Finland gave fans only one real opportunity to cheer, when late-added defenseman Henri Jokiharju beat Connor Hellebuyck clean on a shot 7:31 in to make it 1-0. Hellebuyck stopped the next 18 shots he faced to finish with 20 saves.

The same could not be said for Saros, who allowed six goals on 32 shots and could be replaced in net by Kevin Lankinen for Finland's game against Sweden on Saturday.

"Of course we need to think about that," Pennanen said. "It was a tough day for Juuse. He was really good the first 40 minutes, but I think we need to analyze this game and make those decisions tomorrow or Saturday."

The U.S. does not need to worry about making a switch there, but Sullivan made some keen midgame adjustments that contributed to his team moving to the top of the 4 Nations standings one turn through round-robin play.

During the second period, Sullivan moved Brady Tkachuk to left wing with Eichel and Matthew Tkachuk and sent Kyle Connor to the second line alongside Matthews and Jack Hughes. He flip-flopped his second and third defense pairs to put Noah Hanifin with Adam Fox and Jaccob Slavin with Brock Faber.

"We've been together for four days," Eichel said. "He's coached for quite a while. I think we're all trying to find chemistry and get comfortable with each other. That could mean some changes in lines and pairings and whatnot. I think everyone was prepared when their number was called and helped contribute to the win."