Armed with a new entry in the rulebook, NHL referees will be watching closely for bodychecks that make contact with the head this season.
Officials now have the ability to give out a major penalty for illegal checking to the head -- an offence that comes with an automatic game misconduct. A key component of the rule is that the hit must come from an unsuspecting angle for it to be considered an infraction.
Those type of bodychecks became a major topic of discussion last season after a couple players were sidelined with concussions in vicious-looking incidents.
Back then, the hits were considered legal because they were delivered with a shoulder. A change to the rules over the summer has given referees the ability to penalize them during the 2010-11 season.
"There's going to be a bit of a learning curve," said Terry Gregson, the NHL's director of officiating. "The key at training camp we talked about was the fact the first criteria is it must be from the blindside. We went over a number of videos at camp, we went over the language of the rule and we talked about the fact we're taking an element of shoulder checking and making it illegal now.
"We have a specific rule for it, as opposed to before when you almost had to be a little bit creative if you thought (a hit) was over the top."
Ultimately, it won't be a major adjustment for the men in charge of enforcing the rules.
There tends to be very little subtlety with the type of hit that has been outlawed. They typically happen in open ice on a player who is carrying the puck.
"This is very different from when we introduced the obstruction rules," said Gregson. "That was really something that was almost a tactic in every second of every game, whereas this is more of a devastating type of hit that I think (referees) are going to recognize."
The NHL distributed a video outlining the rule changes to its 30 teams. Every player was shown it during training camp.
The movement for change started growing after Florida Panthers forward David Booth suffered a serious concussion in a blindside bodycheck from Philadelphia's Mike Richards last October. Booth was limited to just 28 games as a result and is a big supporter of the new rule.
"It needed to be done," said Booth. "There were a lot of injuries last season because of it. You have to make the game safer, but you can't take the physical play out of the game because that's what makes the game unique.
"They did a good job with it and I think it will prevent some injuries."
One thing Gregson wants referees to be aware of is any changes that may happen in the game as a result of the new penalty. The league's video covered low hits because there's a feeling that they could increase as players intentionally avoid throwing bodychecks that make contact with the head.
Referees will also be on guard for players who might try to embellish a head hit.
"(They'll be) watching for the head snap," said Gregson. "When a shoulder comes within a half an inch of your chin and your head's flying back -- well, you know what, I'm going to tell you right now there's going to be a couple of our guys get fooled because of a sight line.
"Those are things we're going to guard against." He also acknowledges that his men are only part of the equation.
NHL disciplinarian Colin Campbell will have the authority to suspend players who throw blindside hits to the head.
"To me, the real teeth of this rule is now the supplementary discipline," said Gregson. "Everyone judges everything in video time except the referees. They have to judge it in real time."
The NHL employs 33 full-time referees, including Bill McCreary, who is set to work his 1,600th career regular-season game. McCreary had originally planned to retire but was asked by Gregson to stay on for another year.
During the off-season, Gregson hired two new referees -- Jean Hebert of Moncton, N.B., and Sweden's Marcus Vinnerborg. They'll be among six officials who work in both the American Hockey League and NHL this season.
Vinnerborg will become the first European official to work an NHL game once he gets an opportunity. He'll get plenty of seasoning in the minors before that happens.
"The physicality of the game of the game here is very different from in Europe," said Gregson. "There's a lot more cycling in Europe and things like that. Where here, the bodychecks are there. We just want to make sure that he adapts to that and he's fully aware of that.
"It's all a learning curve, no different than when a team brings a player over from Europe."
Gregson likes to view the officials as one big team.
Another message he delivered during their training camp in September was keeping up the standard that was established coming out of the lockout five years ago. The sport is in a good place and he wants to make sure it stays there.
"There's always going to be testing behaviour," said Gregson. "Players and teams are going to push (the limits), we have to push back just as hard for the integrity of the game."