PRAGUE — There are plenty of determining factors that go into whether a team looks to sign a player, whether in free agency or through the process of re-upping their own guys. One factor that can turn an enticing player into a heaping bowl of plutonium is the three most dreaded words in all of sports: history of concussions.

Patrice Bergeron, who on Friday agreed to a three-year extension with the Bruins worth $15 million, unfortunately is quite familiar with concussions, having suffered a brutal Randy Jones hit from behind on October 27, 2007. Just 10 games in, Bergeron was done for the season and would not return until the following campaign.

“I still remember that arena being so quiet as a coach, and the players. Really it seemed to rattle the whole bench. The first thing you want to do when the game is over is not even talk about the game, but go and see him and make sure that everything’s fine, because it was a real close call. It was one that could have easily ended his career,” Claude Julien said on Friday. “The thing that we really wanted to do was make sure that the person was taken care of first and foremost.”

Julien added that despite Bergeron wanting to return for the playoffs that season, much like Marc Savard did this past season, the Bruins decided that taking the entire season and offseason to get his health in tip top shape was the safest route for a guy who was just 22 years of age and dealing with such a serious injury.

“We were going to be as patient as we needed to be, we were going to be as supportive as we needed to be,” Julien said. “He never played the rest of that year. I know at one point he wanted to come in and play in the layoffs, but at that point we made a decision that it would be better off not to and wait a little bit more.”

Bergeron spoke on Friday of how much the team looking after his wellbeing rather than trying to get as much production as they could meant to him. Sitting at his press conference at O2 arena in Prague, he made it clear just how respected and valued the team’s treatment of him feel in the post-concussion process.

Of course, the Jones hit would not be the last of Bergeron’s dealings with concussions. A December 2008 collision with Dennis Seidenberg, then of the Hurricanes, left him once again flat on the ice with what would later be determined to be his second concussion in the span of 15 months.

Julien said that it was natural to “start worrying again” after the Seidenberg collision, but gave Bergeron much-deserved credit for letting things like his two-way style of play, as well as his leadership, define who he’s been as a player rather the concussions. As the Savard situation has illustrated all too clearly, concussions are a messy affair, and one that makes projecting the future almost impossible. With Bergeron primed for a big season and still with room to grow offensively, the Bruins couldn’t have hoped for a better result in wake of two of the darker moments in recent franchise history.