One can go all the way back to last summer and see how much Marco Sturm was concerned about the penalty kill.

Early in the season, it looked like new Bruins’ coach worries about the kill would pay dividends. But after a good start to the season on the PK, the B’s have tumbled down to 28th in the NHL, killing just a 76.4% success rate.

Trying to fix the kill was some of the coaching staff’s most important “homework” for the extended Olympic break, said Sturm upon the players’ return to the Warrior Ice Arena for practices last week.

The most obvious thing they have to do is cut down on penalties. Their plummet toward the bottom of the PK rankings has – surprise, surprise – coincided with them shooting up in the “minor penalties taken” category. They have taken 243, second only to the Florida Panthers’ 255.

But it also sounds like they plan to tweak their diamond structure as well. What exactly they will be doing differently is hard to tell in practice, especially with the fluid nature of the sport. But Sturm said it’s all part of the season-long chess match between the league’s power plays and penalty kills.

“Power plays get better. They do. If you look at us at the start, we were all out and we did exactly what we wanted to do. The things is, after a certain time and certain games – (assistant coach Steve) Spotter calls it a ‘copy league’ – what it means is you can…see certain weaknesses on the PK,” said Sturm. “With the diamond, they got us pretty much and we just couldn’t handle it and didn’t have an answer. And also we were taking way too many, too. That was a little bit of the downfall. Again, we try to have something in place right now that hopefully fits our group and players better.”

The diamond, he said, giveth and taketh away.

“What I really like on the diamond is you take away the one-timers,” said Sturm. “The old way (the four-man box), the flanks were always available. You think about (Alex) Ovechkin and all those guys, you kind of take that away. You can be very aggressive. But you will give up probably the low 2-on-1s. That would be the downside of it. And now guys slowly figure out how to beat it, any system. That’s what can happen, and it’s already happening, so that’s why we want to be ahead of the curve a little bit.”

Going into the season, the first order of business was to identify some players who could kill, especially after the team traded away PK stalwarts Brad Marchand, Charlie Coyle and Brandon Carlo at last season’s trade deadline. The regulars on the back end are Nikita Zadorov, Charlie McAvoy, Hampus Lindholm and Andrew Peeke. Up front, there are stalwarts Sean Kuraly, Mark Kastelic, Pavel Zacha and Elias Lindholm. But rookie Fraser Minten and Tanner Jeannot, who had not killed in several years, are also heavily in the rotation. Sturm feels he’s got the personnel to do the job, though he said he could mix up the pairings.

Kuraly leads all forwards in PK time a game at 3:05 a game and he’s done it throughout his career. Pinpointing any one area as the problem, he said, is futile.

“We were on a roll earlier in the season. Does that mean power plays figure out what we’re doing and we didn’t adjust well enough? I don’t know. It’s a culmination of a lot of things,” said Kuraly. “As players, you definitely take it on to yourself to think of what we can do better. It’s just all the little things. Can we win more faceoffs and get more clears? On clears, can we do cooperate clears and share on our clears? Can we be a little bit better up ice, be a little stiffer and put ourselves in a better spot? Can we be better with our stick detail? Can we communicate better.

“I think it’s a culmination of all those things. They look at all these numbers and all these stats and if it was one thing, I think it would be pretty easy to clean up or at least address. I think it’s just a culmination of all those things to make a penalty kill good. And I think can we get on and off the ice and change quick is part of it. A lot of things make a penalty kill good. Of those six or seven things, if we can improve them five or 10 percent, we could have a really good penalty kill.”

Like those of us on the Garden’s ninth floor, players on the kill can often see on video after the fact they had more time on a play. Communication, said Kuraly, is huge.

“Just by saying a few words, and I always talk with my linemates,” said Kuraly. “David Backes was the one that insisted I do that a long time ago, you make them look better if you just throw any sort of communication at them. “Time” or “take a look,” “heads up.” It’s pretty primitive what you can say to them. Just give them a clue, even if you think it might not help. There’s a lot of times where, even if you tell a guy he’s got some time, you settle down a little more and make just a little bit better play.”…

Charlie McAvoy will be taking a crack at his dream on Sunday morning when he and his USA teammates take on Canada for the Olympic gold medal. Sturm, though, is a little nervous about how he’’ll be able to transition back NHL hockey, which restarts for the B’s on Thursday with a big game against Columbus.

“Knowing Charlie, I know this is something he’s been looking forward to, probably his whole life. I know he will be great,” said Sturm. “I know it’s going to be a challenge (upon his return). From my experience coming back, the mental part of it is just, because you’re so emotionally involved in those Olympics, it drains you…it’s going to be a challenge, especially Charlie because he plays a lot…It’s a mental drain and that’s why we just have to manage every day the right way so we can have the best outcome.”…

Pavel Zacha appears on schedule to be ready to play next Thursday against the Blue Jackets. He was able to shed the non-contact jersey for the regular sweater on Saturday.