The Bruins had collapsed in the first round of the 2004 playoffs against an undermanned Montreal Canadiens team, blowing series leads of 2-0 and 3-1 along the way. Thornton had zero points while quietly suffering from a rib injury. He was barely visible on and off the ice, prompting a respected Boston columnist to suggest Thornton cash in the coveted captain's "C."
In the offseason, top-scoring linemate Mike Knuble shuffled off to Philadelphia as a free agent, following a long line of top-level Bruins driven from the fold for want of cash.
All in all, it looked like Thornton's days in Boston were numbered -- and destined to be played out under a rather ominous cloud.
But what a difference a lockout makes.
Not only did the Bruins re-sign Thornton to a three-year deal worth $20 million, making him one of the NHL's highest-paid players and delaying a trip to the free-agent market next summer, but Thornton also became actively involved in a retooling process that has Bruins fans speaking in hushed tones about a run to the Stanley Cup.
"We talked quite a bit and I had a lot of say in who we got," Thornton said. "Really, the game's changed. You have to have a relationship with the general managers. It makes you a lot closer and the players really have a lot of input nowadays compared to before."
The evolution of the once-tumultuous relationship between Thornton and Bruins management might well serve as a model for how other teams retain their emerging stars and lure others to their teams.
Under the old collective bargaining agreement, the Bruins were reluctant to spend on a par with other big-market clubs, leading to the often-acrimonious departure of popular players such as Bill Guerin and Jason Allison. It looked like Thornton was headed down that same path when the lockout began.
But with the salary-cap system in place, owner Jeremy Jacobs pledged the team would spend to the cap's limits in order to build a Cup contender, and he has, at least on paper, done just that. By inking Thornton to a long-term deal, returning key restricted free agents Glen Murray and Sergei Samsonov while adding unrestricted free agents Alexei Zhamnov and Brian Leetch, the Bruins have remade their image across the NHL while avoiding a potential season-long soap opera regarding Thornton's future.
"The Bruins always said they were going to change after this CBA, and obviously they have. And personally, they've treated me great the past couple of months," Thornton said. "So I'm excited to get back playing with the Bruins and I know they're happy to have me."
Beyond the financial elements of the deal, Bruins general manager Mike O'Connell broke down the traditional barriers between players and management, discussing potential moves with Thornton, at one point traveling to Thornton's home near London, Ontario, to talk about them.
"I wanted to make sure Joe understood what everything meant, not only to him but to the team," O'Connell said. "I tried to get him involved in the process. To let him know what kind of team we were trying to put together was very important."
The day before the Bruins signed veteran forward Travis Green, Thornton had been on the phone from Canadian Olympic orientation camp with O'Connell, talking about Green's role on the team. Previously, Thornton had been privy to ongoing efforts to land Mike Modano and other top players.
"I think we're going to be great," Thornton said. "Zhamnov will be the second-line center, Dave Scatchard is the third-line center, we've got Sergei coming back, Glen Murray, Leetch back, one of the best young goalies in [Andrew] Raycroft, so we're definitely going to be one of the better teams in the East. I feel really confident in the team we've got right now."
If the dynamics surrounding the team and Thornton have been dramatically altered, the one thing that will not change is that Thornton remains the team's fulcrum. This will certainly be the strongest supporting cast Thornton has seen since arriving as the No. 1 overall draft pick in 1997, but if the Bruins challenge for their first Stanley Cup since 1972, it will be because Thornton has led them there.
And therein lies the challenge for Thornton.
All of the ancillary issues have been resolved: contract, future, supporting cast. Now, Thornton must deliver the goods.
No longer is it enough to put up big numbers. It is about winning and scoring at the right time.
"I think there is an expectation. And I think they're the expectations Joe has of himself," O'Connell said.
The Bruins' GM likes to invoke the names of two Hall of Fame-bound captains -- Scott Stevens in New Jersey and Steve Yzerman in Detroit -- as models for what he hopes will be Thornton's evolution in Boston. Both were offensive forces early in their careers and both men changed their game, sacrificing point totals to become more complete players. Both delivered crucial performances in winning three Cups apiece between 1995 and 2003.
"Both are great captains," O'Connell said. "It takes time. It just doesn't happen [overnight]."
Thornton has proved he can score, O'Connell said, adding: "Now it's really about how important winning is to him and the team around him. That's where Yzerman and Stevens really stepped forward."
Thornton already appears to have taken at least a small step down that road.
Since the end of the '04 playoffs, Thornton has played alongside the game's most talented players and most respected leaders in the World Cup of Hockey, the World Championships, and most recently, at the Canadian Olympic orientation camp in British Columbia, where he was one of the standout performers.
During the World Cup of Hockey, Thornton's first taste of a best-of-the-best tournament featuring NHL players, he assumed a more understated role with a powerful Canadian squad. He did so willingly, and turned out to be a key two-way presence for a team that went undefeated through the tournament.
"I think he's still in a growing stage," said Pat Quinn, who coached the World Cup team and will return to his role as Olympic head coach at the Torino Games. "Based on last year's World Cup, he was a guy that still had some habits that young guys seem to have and he was asked to change them, and he went about making that adjustment, and it looks like he's carried it right on. It's just stages of development that young guys go through."
For his part, Thornton seems comfortable with both his past and his future.
He says he feels no added pressure heading into this season, nor does he feel the need to adjust his game just to meet the expectations of others.
"I have the highest expectations of myself. Nobody can put higher expectations on myself. I'm looking forward to the challenge," Thornton said. "Obviously, I think my game's getting better each and every year. I feel more comfortable out there, more confident. I think it's getting better and that's obviously going to bring you more confidence, more leadership, as well."
Even a reminder of that ill-fated playoff series in 2004 brings a wry grin to Thornton's face.
"There's been so much hockey since then," he said. "World Cup, played over in Switzerland, World Championships. So that's way back in the past.
"I'm just looking for the future, and apparently, we've got a bright future."
Scott Burnside is a freelance writer based in Atlanta and is a frequent contributor to ESPN.com.