The 2005-06 NHL season was a disaster for the Boston Bruins.

They traded away superstar center and captain Joe Thornton to the San Jose Sharks early in the campaign for a lackluster return package. The team lacked talent and toughness, and it finished with the fifth-worst record in the league.

The franchise, which hadn’t been a real Stanley Cup contender since the late 1980s and early 1990s, appeared to be light years away from ending its championship drought, which in 2006 stood at 34 years.

It was, essentially, rock bottom for the Bruins.

And then everything changed July 1, 2006.

That’s when the Bruins, who were not big spenders at the time, splashed the cash to sign star defenseman Zdeno Chara to a five-year, $37.5 million contract. It’s without question the best free agent signing in league history.

“I’m willing to lead by my example of hard work, dedication, discipline and drive,” Chara said in his introductory press conference in July of 2006.

He also made it clear in that press conference what the objective was for him and the team: “I think the only thing we care (about) is the final goal and to win at the end.”

The Bruins will retire Chara’s No. 33 to the TD Garden rafters Thursday night before the B’s play the Seattle Kraken. It’s a fitting honor for a player who transformed the Bruins back into a Stanley Cup contender.

But it didn’t happen overnight. Playoff setbacks in 2008, 2009 and then blowing a 3-0 series lead in the second round to the Philadelphia Flyers in 2010 created some doubt over whether the Bruins had what it took to be champions.

But Chara, with his leadership and determination, kept the B’s moving forward. One thing about Chara is he never backs down from a challenge. He looks at the impossible as very much possible.

The Bruins’ 2011 playoff run, which culminated with the franchise winning its first Stanley Cup in 39 years, was one of the most exciting three-month periods in the history of Boston sports. There were so many ups, downs, and memorable moments.

There were many heroes during those four playoff series. Tim Thomas set a record for playoff save percentage and won the Conn Smythe Trophy as postseason MVP. David Krejci led the playoffs with 23 points. Brad Marchand scored a then-rookie record 11 playoff goals, including five in the Cup Final. Nathan Horton scored two OT-winning goals and the only goal in Game 7 of the Eastern Conference Final.

Chara was also at the top of his game. When the Bruins needed it most, their captain stepped up with elite play at both ends of the ice on the sport’s biggest stage.

Chara played an astounding 37:06 of ice time in Game 5 of the first-round series versus the Montreal Canadiens. The Habs did not score and tallied only 14 shots when Chara was on the ice. The Bruins ended up winning in double overtime to take a 3-2 series lead. They won the series in overtime of Game 7.

In the second-round sweep against the Flyers, Chara helped tilt the ice heavily in the Bruins’ favor. Boston outscored Philadelphia 13-4 and generated more than 60 percent of all scoring chances during Chara’s 113:58 of ice time over four games.

In Game 7 of the East Final against the Tampa Bay Lightning, the Bruins had a 16-7 advantage in shots, a 12-5 edge in scoring chances and allowed zero goals during Chara’s 26:43 of ice time. The Lightning only tallied two shots on net when Vincent Lecavalier, Martin St. Louis and Steven Stamkos went up against Chara in that game. The B’s won 1-0 to clinch their first Stanley Cup Final appearance since 1990.

Zdeno Chara and Henrik Sedin

Dave Sandford/NHLI via Getty Images

Dave Sandford/NHLI via Getty Images

Canucks superstar Henrik Sedin struggled to score against Zdeno Chara in the 2011 Stanley Cup Final.

The 2011 Cup Final against the Vancouver Canucks is where Chara’s defensive excellence really played a key role for the Bruins. He put on a defensive masterclass against a Canucks team that won the Presidents’ Trophy, scored the most goals of any team and had the No. 1 ranked power play. Daniel Sedin led the league with 104 points. His brother and linemate, Henrik, had 94.

Neither of those two superstar forwards made a profound impact in the Final. Daniel tallied four points in the series but was held without a point in five of the seven games. Two of his points were garbage time assists in Game 6. Henrik was completely invisible. He scored a meaningless goal late in Game 6. It was his only point of the series.

They couldn’t escape the physicality, long reach and towering presence of Chara. He played about 70 even-strength minutes against the Sedins in that series, per Natural Stat Trick, and Boston outscored Vancouver 5-2 and had a .960 save percentage in those minutes. Chara winning that matchup so decisively was pivotal in the outcome.

The Sedins were power-play maestros, too. Daniel led the league with 42 power-play points in the 2010-11 regular season. Henrik had 35. But in 28 minutes of power-play ice time against Chara in the Cup Final, the twins could only muster one goal — a garbage time tally in Game 6. Vancouver’s potent power play, which was supposed to tip the scale in its favor, was bottled up by the Bruins’ 6-foot-9 defenseman. The Canucks ended up going 2-for-32 on the power play in the series.

Overall, the Bruins outscored the Canucks 15-6 in Chara’s ice time over the seven games. He made a huge impact all over the ice versus a Vancouver team that many experts picked to win the series.

And when the final buzzer sounded in Game 7 and commissioner Gary Bettman brought the Stanley Cup onto the Rogers Arena ice and gave it to Chara, the greatest trophy in sports was lifted higher in the air than it ever had, or ever has been.

Winning the ultimate prize didn’t come easy, but those Bruins teams never did anything easy. There were many times throughout that journey toward winning the Stanley Cup that the B’s could have folded and given up. But Chara was never going to let that happen.

He set an example of hard work and dedication that was contagious. No challenge or setback was going to keep him from delivering on the goal he set during his introductory press conference in 2006. This is why the Bruins had the mental toughness to withstand a lot of challenges against the Canucks in the 2011 Cup Final.

Whether it was Patrice Bergeron getting bitten by Alex Burrows in Game 1 and Boston losing 1-0 on a late goal, or the Bruins losing in overtime of Game 2, or Nathan Horton getting knocked out of the series in Game 3 by a vicious hit, or the team losing 1-0 again in Game 5, or the B’s playing a must-win Game 7 on the road, Chara’s leadership kept his team laser-focused on the No. 1 objective.

Other legendary Boston athletes might have won more championships, or taken home more individual awards. But very, very few made the kind of transformational impact on their franchise that Chara did for the Bruins.

It’s one of many reasons why Chara will always be regarded as one of the best Bruins of all time. And it’s why the 2011 title will always matter a little more than some of the others that Boston teams have won.