Second line struggles in defensive end

BOSTON — One step forward, two steps back.

Extrapolate just a bit, and it’s two steps forward and four in the opposite direction — which was the tale of the Bruins’ second line entering Thursday’s game against the Avalanche.

Generating scoring opportunities — and finishing some — hadn’t been a problem for center David Krejci, right wing David Backes and something like a platoon at left wing, with Tim Schaller and Ryan Spooner. Denying opponents, however, had been an issue: In different forms, the line surrendered four goals between the Bruins’ 4-3, overtime win on Monday against the Panthers, and Wednesday’s 4-3, OT road loss to the Capitals. That doubled the number of goals they’d scored over those two games.

“The goals against … you can’t pinpoint anyone’s fault for that,” said Schaller, who scored his fourth goal of the season against the Panthers, but had been on the ice for three goals against by the time the B’s left Washington. “I think we’re doing fine. We’ve just got to keep getting pucks north [toward the offensive zone].”

Schaller didn’t think the fact that both he (Sabres) and Backes (Blues) have come into the Bruins’ defensive system after years in other organizations has resulted in any confusion.

“No, everything comes natural at this point,” he said. “We got all the kinks out earlier in the season. We’re fine.”

Schaller, however, hasn’t played the Bruins’ system all that often with Krejci and Backes. Spooner was the line’s full-time left wing until only recently, and still sees time there on occasion: Spooner moved into Schaller’s spot in Monday’s third period, and had an assist on Backes’ seventh goal of the season.

Bruins head coach Claude Julien has said that in situations where some extra speed is called for, Spooner is his probable choice to complete the line. Schaller plays when the coach wants the line to have more size and grit.

Backes, who spent the last five of his 10 years in the Blues organization under head coach Ken Hitchcock, doesn’t mind the revolving door.

“I don’t know if I had the same line for a whole game in my previous place of employment, so it’s not unusual to me,” Backes said. “It makes you concentrate on what you need to do personally, and as a line you get a little more success when you do that quick flip.”

Krejci, now in his second season of trying to find a full-time left wing to replace the departed Milan Lucic, wouldn’t mind a little stability.

“You always like to stay with the same [linemates], work on some things in practices and games to get better as a line each day,” Krejci said. “It would be nice to stick together as a line for a while.”

No concussion protocol

Schaller was sporting stitches across the bridge of his nose and a scrape near his right cheek, courtesy of being mashed face-first into the glass on Monday by Capitals winger Jakub Vrana. The latter wasn’t penalized — and neither was Schaller, in a way.

Despite the cosmetic damage, he wasn’t directed to leave the game to go through the NHL’s concussion protocol. “Spotters” have instructed on-ice officials to pull players from other NHL games for observation and testing.

“When [trainer Don Del Negro] and I went out back [to have his facial cuts repaired], he was waiting for the call” from the NHL, Schaller said, “but I guess it wasn’t as bad as we all thought.”

Schaller said he wouldn’t have griped if he’d been held out of the game to be checked.

“[Spotters] are there for a reason, and I think they’re there for a good reason,” Schaller said. “So if they call you out, they suspect something. I like what they do there.”