Each member of the line must be on the ice for a goal to qualifySource: Left Wing Lock CGYJ. GaudreauS. MonahanM. Ferland251267.6 Goals BOSB. MarchandP. BergeronD. Pastrnak21387.5% TORZ. HymanA. MatthewsW. Nylander24972.7 COLG. LandeskogN. MacKinnonM. Rantanen291467.4 NYIA. LeeJ. TavaresJ. Bailey241955.8 The best among the best lines in the NHLThe top 10 lines in the NHL in goals scored while playing 5-on-5, by percentage of goals for TMLeft wingCenterright wingForVS.For % PHIC. GirouxS. CouturierJ. Voracek231069.7 For the first couple months of the season, the Boston Bruins had more problems than they could handle. They had lost more games than they had won. They were firmly out of the playoff picture. Top-line center Patrice Bergeron and his linemate Brad Marchand had both missed time with injuries. So had second-line center David Krejci. Goalie Tuukka Rask was a husk of his former self, and looked for a moment as though he might lose his starting job. Matt Beleskey, who the Bruins decided to pay $19 million because he had a handful of good weeks during the spring of 2015, had been placed on waivers.1He cleared them and now plays for Boston’s AHL affiliate in Providence.This was a team that had won the Presidents’ Trophy as recently as 2013-14, and that had a core made up of several skaters who’d played in two of the past seven Stanley Cup Finals. This was also a team that had failed to qualify for two of the past three postseasons, and that hadn’t won a playoff series since they beat the Detroit Red Wings in the spring of 2014.But since a loss to the Washington Capitals in mid-December, the Bruins have been damn near untouchable: They are 14-0-4 in their last 18 games. The Bruins looked like basement dwellers a few months ago, and now pundits are wondering whether they’re legitimate Stanley Cup contenders. But are they for real, or is this streak just a tantalizing aberration?The Bruins are a balanced hockey team — seven skaters have at least 25 points — but much of their recent form can be attributed to the extraordinary play of a rejuvenated Rask and the top line of Bergeron, Marchand, and David Pastrnak, which has established itself as one of the best in the NHL.In his last 18 starts, Rask has lost exactly zero games in regulation; in his prior 13 starts, he had won just three. During his recent dominant stretch, Rask has stopped 94 percent of the shots he’s faced; during his disastrous stretch, he stopped just under 90 percent of the shots he faced.2Not what you’d expect from the NHL’s all-time leader in save percentage.Goaltender play is notoriously unstable, so these gulfs in Rask’s performance aren’t actually as shocking as they seem on the surface. Even if Rask’s save percentage regresses and he stops roughly 92 percent of the shots he faces for the rest of the season, the Bruins will be in good shape.To explain the dominance of Marchand, Bergeron, and Pastrnak, the best place to start is their possession numbers. Bergeron is yet again among the league’s elite faceoff takers, winning more than 57 percent of his draws.3That number drops a bit to roughly 53 percent on power play draws, but Bergeron can be forgiven — unless he’s the man in the penalty box, teams often task their best faceoff man with taking draws on the penalty kill. Among qualifying skaters, all three on Boston’s top line rank in the top 50 in Corsi percentage,4Adjusted for score, zone and venue. which estimates a player’s possession rate by measuring the percentage of shot attempts directed at his opponent’s net versus his own net while he’s on the ice. And because the Bruins’ top troika are sending so many shots toward their opponents’ nets, all three also rank in the top 15 for goals per 60 minutes.Among lines that qualify, only 11 others in the NHL have a higher combined shooting percentage than the combination of Marchand, Bergeron, and Pastrnak. And their goals for percentage — which takes the total number of goals scored while a line is on the ice together and calculates the percentage of those goals that were goals scored by the line — is by far the best in the league. LOSA. IafalloA. KopitarD. Brown201360.6 TBLV. NamestnikovS. StamkosN. Kucherov261957.8 DALJ. BennT. SeguinA. Radulov201360.6 VGKR. SmithW. KarlssonJ. Marchessault321666.7 None of this is to say the Bruins are a one-line team — they’re far from it. Rookie forwards Danton Heinen and Jake DeBrusk have already chipped in with 11 goals each, and rookie defenseman Charlie McAvoy5McAvoy recently underwent minor surgery to correct an abnormal heart rhythm, but is expected to return in two weeks. is building a solid case for the Calder Memorial Trophy. And David Krejci is a pretty decent second line center, too: He’s scored 24 points in 29 games, and he’s winning 56.3 percent of his faceoffs, by far the best mark of his career.Boston will lose in regulation again — Marchand, who is serving a five-game suspension, and McAvoy’s temporary absences should ensure this happens sooner than later. But there’s nothing in recent memory suggesting Boston’s top line will cease to be a possession beast any time soon.6All three forwards finished in the top ten in Corsi percentage in 2016-17. If they keep getting (and burying) their chances — and if Rask’s ascendancy holds up, which his dazzling career implies it might — the Bruins might find themselves playing hockey in June again.