BOSTON -- The Boston Bruins need the Mason Lohrei they got in Thursday's second period. At 17:10, while working the point on the No. 2 power-play unit, Lohrei scored his first goal of the season to tie the game against the Anaheim Ducks 3-3.
The Lohrei that wilted a period later is not one they want to see.
The 24-year-old defenseman was on the ice for two third-period goals against, including Troy Terry's winner in the Bruins' 7-5 loss. Two nights earlier, the Florida Panthers scored two of their three five-on-five goals on the Bruins with Lohrei on the ice.
When Lohrei is with Charlie McAvoy on the No. 1 pair, he has nowhere to hide. McAvoy is the Bruins' best defenseman. As such, coach Marco Sturm needs McAvoy to defend top players.
Sturm had no choice, then, but to put Lohrei elsewhere during Friday's practice at Warrior Ice Arena. Michael Callahan, promoted from Providence on Tuesday, took Lohrei's spot on McAvoy's left side. Lohrei practiced with Andrew Peeke.
Those pairs may stick Saturday against the Colorado Avalanche. Sturm cannot afford to put Lohrei with McAvoy, especially against the team (5-0-3) he classified as the best in the league, until the left-shot defenseman plays his way out of his defensive spiral.
"He is what he is," said Sturm, referring to Lohrei's offensive strengths and work-in-progress D-zone presence. "If you're not sprinting, you're not a sprinter. If you're in the marathon, like (Zdeno Chara) right now, you're a marathon runner. You will not change that. But you can change how simple you're going to play the game, how you're going to respect the game. It's a hard league.
"He has to understand just to focus on his job and doing nothing crazy. Just simplify things. He cares. He wants to do something special. He wants to do more than he should be. That's where he gets into trouble."
Lohrei likes to push the pace offensively. But he is not helping his team if he cannot play firmly in the defensive zone. Lohrei is thinking instead of acting, and it's costing his team.
Lohrei is not alone.
As of Friday, the Bruins have allowed a league-high 24 five-on-five goals. They had given up 61.85 shot attempts per 60 minutes of five-on-five play, per Natural Stat Trick, third-highest in the NHL.
Sturm spent part of Friday morning in the video room with his players. He showed them clips of where they've gone wrong in front of their net. The Bruins, who are still adjusting to Sturm's hybrid system, have been getting caught in between. It will take more time for their defensive assignments to become second nature.
"These guys have been together for four to seven years," said Sturm of lifelong Bruins such as McAvoy and David Pastrnak. "We've only been together for six or seven weeks. They never played a different system. Don't forget that. I can get mad at those guys, my players, as much as I want. I am. But at the same time, I have to realize they've never played a different system. Never. So you've got to be patient."
Previous coaches Joe Sacco, Jim Montgomery and Bruce Cassidy had the Bruins playing zone. Their priorities were layers and net-front coverage. Centers had the green light to lend a hand in puck battles in the corners.
Sturm prefers his players to execute man-on-man coverage when the puck is high in the defensive zone. They do not switch assignments.
Even if an opposing forward, for example, is handling the puck at the blue line, Sturm wants someone in tight coverage. The point is to reduce enemy puck possession.
"That's something we showed today," Sturm said of the video session. "We want to close a little bit faster. We want to outnumber teams. It doesn't matter which area of the zone. Right now, we're just a little bit hesitant. That's why we got caught a couple times in between."
Sturm has them playing zone when the puck is closer to the net. So far, the reads have not been automatic.
"It's just everyone being on the same page," Peeke said. "It's always not just one guy. It's a five-man unit. That's a big thing for us and how we defend. We have layers. There's going to be mistakes in the game. When that happens, there's going to be a guy to support you."
The Bruins are short-handed on the blue line. Hampus Lindholm (lower body) practiced Friday. But Sturm did not make it sound like Lindholm would be available against Colorado. Lindholm has missed six of the past seven games. Jordan Harris is on injured reserve after getting hurt against the Panthers.
The Bruins expected their defense to be their strength this season. It's been the opposite. The Avalanche could be the latest opponent to feast on their weakness.