They were roommates, friends, and countrymen.

Above everything else, Zach Werenski and Brandon Carlo were partners.

In January, Werenski and Carlo starred in Helsinki for Team USA in the World Junior Championship, the top collection of teenage talent. Auston Matthews, he of the four-goal NHL debut, was one of their teammates. Patrik Laine, the No. 2 pick after Matthews in the most recent draft, was Finland’s offensive centerpiece.

The Americans won bronze. One reason they returned from Finland with medals was because Werenski, Columbus’s first-round pick in 2015, and Carlo, one of the Bruins’ three second-round selections that year, served as the best defensive tandem of the tournament. In seven games, Weren­ski scored two goals and seven assists. Carlo added two goals and two assists. They scored their points while playing against every top line.

“We got a lot of minutes together,’’ said Carlo. “Overall, I think our games complemented each other pretty well. He’s a very good offensive defenseman. He definitely works his way up into the play. He can come back and cover himself as well. He actually gave me the opportunity to get up in the play as well, which was nice. Moving the puck with him made it a lot easier on me because he makes really good decisions with the puck. Overall, I think our games complemented each other well. It’s a lot of fun to play with him. I imagine it will be a lot of fun to play against him as well.’’

The latter scenario came true on Thursday at Columbus’s Nationwide Arena, where both made their NHL debuts in the Bruins’ 6-3 win. Weren­ski manned the left side of the Blue Jackets’ first pairing next to ex-Predator Seth Jones. Carlo patrolled the right side with Bruins captain Zdeno Chara occupying the left.

If both continue to develop on their current trajectories, it’s possible the Americans (Werenski is from Grosse Pointe, Mich., Carlo is a native of Colorado Springs) find themselves together again in international play — this time on Team USA’s men’s team.

As a pair, they represent the new standard of shutdown tandem. It used to be that coaches built their top defense-first combinations with strength and surliness in mind. It was that way in 2011, when Claude Julien brought Chara and fellow strongman Dennis Seidenberg together to take on Montreal, Philadelphia, Tampa Bay, and Vancouver. In 2013, the Blackhawks beat the Bruins partly because of the play of their most defensive-minded combination: Niklas Hjalmarsson and Johnny Oduya, not Duncan Keith and Brent Seabrook.

In comparison, Werenski and Carlo represent the defensemen of the future. They’re 19 years old. Both are big (Werenski is 6 feet 2 inches, Carlo 6-4). They skate well. They process the game rapidly. They defend primarily with their feet and sticks and heads, not just their bodies.

It still helps defensemen to be strong and mean. Forwards think twice about dipping their toes into the net-front danger areas when spine-crackers such as Shea Weber, Radko Gudas, and Brooks Orpik are flexing their muscles. A slender puck-moving defenseman such as Erik Karlsson isn’t equipped to handle John Tavares when he turns his back and does his best Kevin McHale imitation in the paint.

But where mobile defenders such as Karlsson excel is at denying forwards from handling the puck in close quarters in the first place. The most efficient manner of defending is gaining control of the puck and going the other way before opponents have a chance to go to work in dangerous areas.

In their amateur postings (Werenski played at the University of Michigan, Carlo elected Tri-City of the WHL) and during training camp, the two teenage defensemen showed they are good at playing defense in a progressive instead of passive manner.

Werenski, the No. 8 overall pick in 2015 and the third defenseman drafted after Noah Hanifin and Ivan Provorov, is the more offensive-minded of the two. The left-shot Werenski is clicking when he’s up the ice with the puck on his stick. He can carry it through the neutral zone and across the blue line. If things go sideways, Werenski is fast enough to backtrack, reset, and put his stick and body back in defending position.

“We don’t want them to be sloppy,’’ Columbus coach John Tortorella said of Werenski and the team’s other young defensemen. “We want to let them play and let them create. We’ll teach the other side of the puck. But on the offensive side, we want them to go.’’

In comparison, Carlo plays a more reserved game. He does not have his ex-partner’s handle of the puck or comfort at rushing it up the ice. But Carlo is good at closing on puck carriers, using his stick to pick their pockets, and triggering the counterattack for his teammates.

“I loved playing with Brandon,’’ Werenski said. “He makes the game so much easier on his partner. He talks. He’s so sound defensively. He always seems to be in the right position to make the right play. That’s all you can ask for in a D partner. I think he was a perfect partner for the World Junior tournament.’’

There are examples of previous cerebral shutdown pairs. In 2008, the last time Detroit won the Stanley Cup, nobody classified Nicklas Lidstrom and Brian Rafalski as thumpers. It didn’t matter. They defended when necessary and moved the puck so rapidly that they rarely had to lean on their opponents.

The NHL’s best pairings dictate play by controlling the puck: Victor Hedman and Anton Stralman, Jake Muzzin and Drew Doughty, possibly Roman Josi and P.K. Subban. When the puck is on a progressive defenseman’s stick, opponents are not equipped to score. The best defense is a good offense.

NOT IN THE PLANS?

Jacobs lukewarm on next Olympics

As chairman of the NHL’s board of governors, Bruins owner Jeremy Jacobs speaks with a powerful voice when it comes to matters of international competition. The NHL’s most time-sensitive global issue is whether it will give its players the green light to play in the 2018 Olympics in Pyeong­chang, South Korea. As of now, Jacobs is lukewarm on NHL participation, especially framed against the World Cup of Hockey in Toronto.

“I’m not that thrilled about going to Korea or anyplace like that,’’ Jacobs said of the 2018 destination. “I don’t think it does anything for our game. I think what we saw in Toronto was really effective. What we see in the future, maybe China might be a possibility.’’

Jacobs is not the only owner who is hesitant about the 2018 Winter Games. The NHL would have to close its doors midseason. It would not have control over television rights. The league would be partly responsible for travel costs of shuttling players, coaches, and personnel to Pyeongchang. South Korea does not represent as much potential as China in growing the league.

Such concerns will not exist with the next iteration of the World Cup. The tournament had its issues, as any reboot of a 12-year-old format would. ESPN’s ratings went in the tank when Team USA failed to qualify for the semifinals. The tournament was competing with football’s start and baseball’s stretch run. Team Europe’s advancement to the final muted fan excitement. Even in Toronto, buzz for the World Cup did not reach a heightened din.

But the NHL had full control of the World Cup. Last month should serve as a learning experience for the tournament’s next arrival.

“We were all very excited to see what it did for the game,’’ Jacobs said. “I think we can do more if we continue this process. I think the World Cup was a step in the right direction. I really do.’’

ETC.

Matthews not typical rookie

Everybody believed Auston Matthews would make Toronto’s opening roster. Nobody thought he would debut with a four-goal explosion.

“Unheard of,’’ said fellow rookie Zach Werenski.

A four-goal game, after all, is the kind of output that had veteran Joe Thornton, of all players, threatening to remove his clothing for an on-ice celebration of production. Under normal circumstances, 19-year-old centers would only score four goals while playing video games.

Matthews, however, is not normal.

He already is playing a man’s game, which he showed in his debut. The goals he scored weren’t flukes. Matthews created his chances with strong, professional, skilled work. Boys don’t strip Mike Hoffman and Erik Karlsson on the same shift, then slip a puck past Craig Anderson. Not even professionals would make such heavy lifting look so simple.

But what coaches have always enjoyed about Matthews is his professional approach. He has always played the game the right way. It’s why, had he been born two days earlier, Matthews might have been picked behind Connor McDavid and before Jack Eichel in the 2015 draft. Eichel may have the higher ceiling. But Matthews already plays a more consistent, reliable, and professional game.

“I think I’m five years older than him, so I don’t think I could have done that at 18,’’ Rob O’Gara, the Bruins’ 23-year-old defenseman, said with a smile. “I know I couldn’t have done that. It was very impressive. Fun to watch.’’

Fresh start for Condon

There is no such thing as job security for backup goalies. Mike Condon learned this the hard way when the Canadiens placed the Holliston native on waivers before the season. It was a likely fate for Condon because of Carey Price’s return and the offseason signing of veteran Al Montoya to serve as the No. 2. Condon started hot after Price’s injury last season. But the former Princeton puck-stopper’s body of work (21-25-6, 2.71 goals-against average, .903 save percentage) was not good enough to spare him from the expected jettisoning. The misfortune of Matt Murray (broken hand), however, played in Condon’s favor, as the Penguins claimed the 26-year-old. Marc-Andre Fleury will be the starter during Murray’s absence, but Condon will be a capable backup until Murray’s return. The Penguins are high on second-year pro Tristan Jarry but do not want to rush the 21-year-old. Condon will once again be the odd man out when Murray comes back. Such is life in Condon’s line of work.

Wings are regular waivers losers

The Red Wings wanted to slide Teemu Pulkkinen through waivers and back to Grand Rapids, their AHL affiliate, where the right-shot forward torched opposing goalies for 34 goals in 46 games in 2014-15. Pulkkinen did not make it to Grand Rapids, as Minnesota claimed the 24-year-old on Wednesday. Pulkkinen was just the latest in waivers casualties who were once Detroit property. Just three days earlier, Carolina claimed Martin Frk. Last year, the Bruins nabbed Landon Ferraro before he cleared and could report to Grand Rapids. In 2014, Carolina claimed Andrej Nestrasil from the Wings on waivers. Detroit GM Ken Holland’s philosophy is to bake his prospects, so to speak, in the AHL until they are ready for consumption in the NHL. One of the drawbacks is that it sometimes takes more than three years of AHL apprenticeship before Holland and his colleagues feel their prospects are ready. By then, they have to clear waivers to return to the AHL. Sometimes they don’t make it through.

Campbell out of NHL

The Bruins did not have a chance to say hello to old friend Gregory Campbell on Thursday in the season opener against Columbus. Two days earlier, the Blue Jackets placed the ex-Bruin on waivers, where he went unclaimed. Campbell might return if Columbus goes through injury trouble. But for now, the depth center is an AHL outcast, like players of his profile (32-year-old grinder making decent cash) can become. It’s not Campbell’s fault that Columbus gave him a two-year, $3 million contract after the Bruins let him walk after 2014-15. The Jackets, however, should have known better than to extend such term and dough to a player with Campbell’s skill set. It’s hard for any team to pay a fourth-liner that kind of money and invest multiple years in a position that is easier to replace than those higher in the lineup. In some ways, Campbell is lucky. Had he signed just a one-year contract with Columbus, he might be out of work. Instead, he’s cashing $1.3 million in salary to play in the AHL, which is better than being unemployed. But it’s a tough thing to accept for a player who’s earned the respect of every coach and teammate.

Gretzky back in Edmonton

Edmonton brought back Wayne Gretzky as partner and vice chair of Oilers Entertainment Group. The Great One joins younger brother Keith Gretzky, Edmonton’s assistant GM. No. 99 will not be involved in hockey operations, but things can always change. Former Bruins GM Peter Chiarelli has the security of the same position in Edmonton as well as the added title of president of hockey operations. But Chiarelli ended up on the wrong end the last time his employer tabbed a former icon. The Bruins hired Cam Neely as vice president in 2010. Five years later, Neely, having been promoted to president, dismissed Chiarelli.

Pirri is a bargain pickup

One of the league’s biggest mysteries is why some GMs have declared Brandon Pirri radioactive. In 2014-15, after being acquired from Chicago, the left-shot Pirri scored 22 goals in 49 games for Florida. Last season, the Panthers shipped Pirri to Anaheim at the trade deadline for a 2016 fifth-rounder. The Ducks declined to make Pirri a qualifying offer this offseason, making him an unrestricted free agent. The 25-year-old didn’t find work until Aug. 25, when the Rangers signed the wing to a one-year, $1.1 million deal. Pirri has a wicked shot and can keep up with the pace. He recorded a goal and an assist in his Rangers debut while playing just 10:57. Coaches don’t like streaky one-dimensional scorers, which Pirri can be at times. But his skill is worth the price.

Loose pucks

If any team were to claim Seth Griffith when the Bruins placed the right wing on waivers, it would have been Toronto. Maple Leafs assistant general manager Mark Hunter is the co-owner of the London Knights, Griffith’s former OHL team. Hunter coached Griffith in 2011-12 when brother Dale Hunter left to take over temporary residence behind the Washington bench. Griffith led the Knights in scoring that year with a 45-40—85 line, more points than ex-teammates and current NHLers Vladislav Namestnikov, Max Domi, Andreas Athanasiou, and Austin Watson. Griffith was a healthy scratch for Toronto’s opener . . . Jonathan Quick will be on the shelf for several weeks after suffering a lower-body injury during the opener against San Jose. Given Quick’s helter-skelter style, it’s a miracle he doesn’t pull his groin every other game. No other goalie performs a nightly gymnastics routine like Quick . . . Buffalo started the season without Jack Eichel, sidelined for a month-plus after spraining his ankle the day before the opener. The Sabres lost Evander Kane in the first game. No city deserves this kind of bad luck.

Fluto Shinzawa can be reached at fshinzawa@globe.com. Follow him on Twitter @GlobeFluto. Material from interviews, wire services, other beat writers, and league and team sources was used in this report.