N.H.L. general managers will be under intense public scrutiny when they convene for their annual meeting in Boca Raton, Fla., beginning Monday. Under pressure from medical researchers, owners and even players, the general managers are expected to strengthen Rule 48, the league’s bylaw governing checks to the head, which was instituted this season.

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But they will probably not establish a ban on head contact like the rule in the International Ice Hockey Federation, the Ontario Hockey League and the N.C.A.A. After speaking to all 30 G.M.’s last week, Bob McKenzie of the Canadian network TSN reported that they were likely to stop short of a ban, but the movement toward more stringency is palpable.

At last year’s meeting, the general managers came up with a draft form of what became Rule 48, which barred blindside hits to the head and checks that take aim at the head. A steady drumbeat of medical evidence from doctors and researchers showed the damage caused to hockey players from repeated blows to the head, and as recently as a few weeks ago, the league seemed satisfied with what it had done.

Comments by the managers at the board of governors meeting in December indicated that Rule 48 was having the desired effect: deterring players from taking aim at one another’s heads. At the All-Star Game at the end of January, Commissioner Gary Bettman said that although concussions were slightly up this season, the number resulting from head shots was actually down — and he credited Rule 48.

At that time, the top agenda item for the Boca Raton meeting was shaping up to be a possible crackdown on checks from behind.

But a recent pileup of unusually bad, headline-grabbing news put concussion prevention front and center again.

The frightening injury of the Canadiens’ Max Pacioretty after he was shoved into a stanchion by the Bruins’ Zdeno Chara; a recent study that found concussion-induced chronic traumatic encephalopathy in Bob Probert’s brain; and Sidney Crosby’s two-month absence because of a concussion caused both by a hit to the head and by a later check from behind have led to a public outcry in favor of more stringent rules governing head shots, or at least stronger disciplinary measures to prevent them.

In a letter to the N.H.L., Air Canada said that the airline would withdraw its sponsorship if the league did not improve player safety. And in an op-ed article published in Saturday’s Globe and Mail of Toronto and Le Presse of Montreal, Ken Dryden called for the managers to do more to prevent concussions.

“Arguments and explanations don’t matter anymore,” wrote Dryden, the Canadiens’ Hall of Fame goalie of the 1970s and a member of Parliament. “The N.H.L. has to risk taking the big steps that are needed: if some of them prove wrong, they’ll still be far less wrong than what we have now. It is time to stop being stupid.”

A poll last week showed that a majority of Canadians disagreed with the N.H.L’s decision not to suspend Chara for his hit on Pacioretty, and on Thursday the Canadiens owner Geoff Molson took the unusual step of publicly criticizing the league for not punishing Chara beyond a five-minute major and game misconduct.

“We can assure you that we have made our position clear to Commissioner Gary Bettman, and that he has agreed to make this issue a priority at the next general managers meeting,” Molson said in a statement.

Molson said that his team’s general manager, Pierre Gauthier, would be addressing the meeting on the need for longer suspensions, and that he was willing to take a leadership role among the owners to make the game safer.

“Our organization believes that the players’ safety in hockey has become a major concern, and that this situation has reached a point of urgency,” Molson said.

He added, “We understand and appreciate hockey being a physical sport, but we do not accept any violent behavior that will put the players’ health and safety at risk.”

Some players also voiced opposition to the league’s excusing Chara. The Canucks’ Henrik Sedin, last season’s most valuable player, told The Vancouver Sun: “I don’t see the reasoning behind it. Give him at least something to show that’s not acceptable.”

Sedin added he believed Chara, the game’s biggest and strongest player, was aware he was propelling Pacioretty into the stanchion, although he did not intend to seriously injure him.

“It’s gotten to the point, you have to suspend guys if you hit the head,” Sedin said. “You have to do it even if guys say they didn’t mean to do it or it’s an accident. You have to start somewhere. I don’t think players know where the limit is. That’s the bottom line.”

This week, the hockey world will be watching to see whether the general managers establish where that bottom line really is.