For the last two seasons, concussions and hits to the head were frequent talking points in the N.H.L., with the Pittsburgh Penguins star Sidney Crosby serving as the catalyst.
As the lockout dragged on for more than four months, though, the conversation shifted from player safety to revenue percentages and competitive balance. The first few weeks of the shortened 48-game season passed without much talk of concussions.
But in the past two weeks, 11 N.H.L. players are believed to have sustained them, among them Crosby's teammate and the reigning most valuable player, Evgeni Malkin, thrusting the issue of head injuries back into the spotlight.
Concussions continue to plague the league, despite its increased emphasis on reducing them. For the second season, the N.H.L. is playing under its broadened version of Rule 48, which penalizes hits that target an opponent's head or make the head the principal point of contact. But many of the recent injuries, including Malkin's, were not caused by hits deemed worthy of fines or suspensions.
Last season, according to CBC network estimates, about 90 players missed games because of concussions, about 13 percent of N.H.L. players on active rosters on a given night. Crosby missed 60 games while recovering from a concussion he sustained in the 2011 Winter Classic.
Malkin, who has 4 goals and 17 assists in 18 games this season, received a concussion diagnosis Sunday, two days after he fell awkwardly into the end boards following a routine shove from Florida's Erik Gudbranson. Malkin slid back-first into the boards, causing his head to snap sharply backward and strike the boards.
Penguins Coach Dan Bylsma said Malkin initially had short-term memory loss but was improving. The team placed Malkin on injured reserve Monday, retroactive to Sunday. A player on injured reserve is ineligible to play for a minimum of seven days, meaning the soonest Malkin can be reactivated is next Sunday.
"There's not a specific schedule for that right now in terms of physical activity," Bylsma told reporters Tuesday in Sunrise, Fla., where the Penguins played the Panthers again.
"The protocol and resting with a concussion, he's following that right now," Bylsma added.
The Penguins, who lead the Atlantic Division, have a new medical team this season, headed by Dr. Christopher Harner of the University of Pittsburgh Medical Center, where the team is planning to open a training, sports medicine and performance facility. The Penguins announced in the summer that they had ended their association with their longtime team doctor, Charles Burke.
The team and Burke said that their parting was amicable and not related to Crosby's 14-month concussion saga. Penguins President David Morehouse said the team "wanted to have enhanced medical coverage for our players," which included having doctors travel with the team.
Perhaps because of their history with Crosby, the Penguins are among the N.H.L.'s most transparent teams in disclosing concussions, and General Manager Ray Shero is considered a progressive voice in support of tighter rules governing hits to the head and concussion protocol.
A lack of openness about concussions can make it difficult to have an accurate accounting of head injuries. Among the other players with recently announced head injuries are the 20-year-old Carolina forward Jeff Skinner, who missed 16 games last season with a concussion; St. Louis's high-scoring rookie Vladimir Tarasenko; another top rookie, Brendan Gallagher of Montreal; and Devils winger Ryan Carter.
Under N.H.L. regulations, clubs are not required to disclose the specific nature of a player's injury. But they are not permitted to give out false or misleading information about an injury.
The Columbus Blue Jackets' announcement that Artem Anisimov is out with an "upper body injury" is allowed under those guidelines, even though he was taken off the ice in Detroit on a stretcher Thursday after his head was driven into the ice by the elbow of a falling Red Wing, Kyle Quincey.
The Rangers do not always disclose players' concussions. Rick Nash and Ryan McDonagh are believed to be out of the lineup with concussions, but the team has issued no details regarding their conditions. Forward Darroll Powe was sidelined with a confirmed concussion Feb. 17, but returned to play on Tuesday.
Nash, who has missed four games, returned to practice Tuesday and told reporters that his absence was because of a "number of things." He declined to confirm or deny that a concussion was among the injuries.
The Rangers have been reluctant to disclose concussions in the recent past. In January 2011, they revealed that the enforcer Derek Boogaard had sustained a concussion in a fight about a month earlier, and in September 2011 they disclosed that defenseman Marc Staal had played more than two months at the end of the previous season with concussion symptoms. Staal did not return to game action until the 2012 Winter Classic.
