Here's a look at the series of events since Sidney Crosby suffered a concussion in January of 2011.
January 1, 2011
Crosby takes a blind side shoulder to the head from David Steckel of the Washington Capitals. The hit occurs during the second period of the 2011 NHL Winter Classic, an outdoor game played in Pittsburgh. Crosby leaves the game but returns for the third period. Steckel will later claim that the collision was accidental. He is not penalized or suspended for the incident.
Crosby is facing the boards when he is checked by Tampa Bay Lightning defenseman Victor Hedman during a game in Tampa Bay. Despite being visibly shaken by the hit, Crosby finishes the game and travels to Montreal with the Penguins.
Crosby returns to Pittsburgh for medical attention and tests.
The Penguins announce that Crosby will miss a week because of a concussion. At the time, Crosby leads the NHL with 66 points (32 goals, 34 assists) in 41 games. That will be his season total, as Crosby will miss the remaining 42 games of the 2010-11 season and all of the Penguins' playoff games.
Crosby says he will not return to the ice until his concussion symptoms have fully subsided. He suggests that the NHL should be more vigilant about eliminating blindside hits and other dangerous hits.
Crosby's concussion symptoms remain and he is now out of the Penguins lineup "indefinitely." Pittsburgh coach Dan Bylsma tells reporters that he believes Crosby is improving, but will not return to the lineup until symptoms subside.
Pittsburgh general manager Ray Shero describes Crosby's future as "unknown." Shero has already made trades to add players to the lineup, replacing Crosby and other injured players.
Crosby's agent, Pat Brisson, tells ESPN.com that Crosby continues to suffer concussion symptoms, and it's not known whether he will play again this season. "We have to go a day at a time," says Brisson. "Anyone in the media speculating that his season is over is jumping the gun. No one knows."
Crosby skates for the first time since January 5, for about 15 minutes. "I feel good," he says. "It's really early. It's just part of progress and trying to get better. I felt pretty good doing some light workouts. I was told I had the opportunity to skate. I went out there for 15 minutes to see how I felt. I felt good, so that's a good sign."
For the Penguins first game of the 2011 Stanley Cup Playoffs, Crosby sits with team management and staff in the press box. He wears a headset to communicate with the coaching staff on the bench. The Penguins defeat the Tampa Bay Lightning in Game One, but Pittsburgh will later blow a 3-1 series lead and lose to Tampa Bay in seven games.
Crosby says he had a recent setback in his concussion recovery and began experiencing symptoms again. He believes he will be ready for the start of next season.
Crosby is cleared by Pittsburgh Penguins doctors to start begin offseason workouts. Penguins' GM Ray Shero says the goal is for Crosby to resume on-ice workouts later in the summer and return to his "usual routine."
The NHL board of governors approves new rules governing hits to the head: "Players will now face a minor penalty for any hit that involves primary contact to the head and shots that target an opponent's head and make it the principal point of contact."
Crosby joins his teammates for the first day of training camp.
Crosby plays in a scrimmage and works on set plays. It is his first five-on-five hockey since January 5.
Preparing to open the season, the Penguins place Crosby on injured reserve.
Crosby is cleared for contact in practice.
Crosby announces that he will play the following night in Pittsburgh's game against the New York Islanders.
Playing his first NHL game since January 5, Crosby has two goals and two assists as the Penguins defeat the Islanders 5-0.
During a game against the Boston Bruins, Crosby collides with teammate Chris Kunitz and is slow to get back to his feet. During a puck battle in the same game, Crosby takes a glancing arm or elbow from Bruins forward David Krejci. But he finishes the game with no outward signs of trouble.
The Penguins announce that Crosby will sit out two games as a precaution after taking a big hit in a game against the Bruins.
The Penguins announce that Crosby is out indefinitely because of "concussion-like" symptoms. Asked if the Krejci hit may have triggered the setback, he says, "If you had to look at one hit then yeah...if anything it was probably that one. It was a good one." Crosby has 12 points in eight games since November 21.
January 13, 2012
Crosby returns to practice with his teammates, telling reporters that "the symptoms are getting a lot better, but I wouldn't say symptom-free." Crosby begins practicing regularly, but is not cleared for body contact.
The Penguins and Crosby's agent confirm that he has been diagnosed with a soft tissue injury in his neck. He begins treatment to reduce swelling around two vertebrae. Doctors tell him that the injury often causes concussion-like symptoms. It remains unclear whether he is also suffering from a concussion.
Crosby is cleared for contact in practice. He cautiously describes it as a "good step" and says he is symptom-free.
Crosby takes extra practice and tells reporters he needs more practice time to be sure he's ready to return to the lineup. Asked about a possible return for a March 15 games against the Rangers, Crosby replies, “That’s soon, so we’ll see.”
The Pittsburgh Penguins beat the New York Rangers 5-2. Playing his first game in more than three months, Crosby registers two assists in the game.