CLEVELAND -- Paul Pierce has been telling anyone who will listen that the Celtics felt like somebody stole something from them when they didn't get the chance to defend their 2008 NBA Championship at full strength last season.

And while he spent the summer of 2008 showing off his Finals MVP trophy, and came to training camp last year talking about not wanting to be a one-hit wonder, Pierce spent much of his 2009 offseason in Los Angeles hearing about Kobe Bryant and the Los Angeles Lakers, the team the Celtics vanquished in six games just a season before.

The Celtics Captain, who's not afraid to lock himself in the gym on a Saturday night to get up some extra jumpers, spent this summer looking for any edge he could get.

Paul Pierce

Paul Pierce is poised to lead his team toward a second NBA championship in three years..
David Liam Kyle/NBAE/Getty

"We have a mission, and that's to regain our championship," Pierce said in early September, when almost the entire team had already begun working out voluntarily, weeks ahead of training camp. Pierce himself spent quite a bit of time promoting his own "Truth on Health" campaign and looked rested and ready well ahead of camp.

Now, with Opening Night finally here, he is beaming about the team's depth thanks to some shrewd offseason moves.

"When we're healthy, we're the team to beat in the East," Pierce said, already talking about today's matchup with the Cavaliers and wearing a shirt that said "UNSTOPPABLE".

"It's tough, because you're challenged night-in and night-out because you are the champs. You already have that target on your back. " Pierce said of the abbreviated run in 2009. "I think at times we got over-excited that we were the champs of 2008, but at the same time it really meant nothing in 2009. We realized that when we didn't bring home the trophy."

Celtics Coach Doc Rivers, who'd been warned by his former coaches about how hard it would be to take an opponent's best shot night after night, has said that his team lost some of the Ubuntu spirit that united them in their championship run. After a summer of reflection, he found his team's postseason shortcomings to be somewhat revealing.

"I thought the experience of last season was a learning experience for all of us. Being a defending champion and every night, everybody attacking you, it's a great experience to go through, but it's a very difficult one," said Celtics Coach Doc Rivers. "You learn a lot about people, as far as your players and how they handle success. I thought some handled well, and quite frankly, some didn't handle it well."

Kevin Garnett, who watched the entire postseason in street clothes due to a knee injury suffered late in the regular season, counted 2009 among his toughest seasons as a professional.

"It was the first time I've ever been injured. Not hurt, but injured. That was tough for me, just sitting there, because I don't like to sit on the bench, because it's already driving me crazy that I can't play," Garnett said during the preseason, shaking his head and noting that he did his best to be a cheerleader if nothing else.

"One thing that stood out, though, and one thing I learned, is that it takes everybody. You have to have all facets of life lined up. All things, health-wise, chemistry, all those things have to be lined up. You need a little bit of luck on your side," Garnett said. "But from my perspective, it was excruciating, man. It was hard sitting there watching my guys get beat up, trying to fight and claw their way through and knowing physically that you can't do anything about it."

With Garnett back in action and a reloaded roster that's deeper than ever, the mission is clear: win one more title while the window is still open.

Fans, media and even team personnel can argue all they want about how big that opening is, but if recent NBA history has proven anything, it's that things can change in a hurry. The 2006 Miami Heat found that out after winning an NBA title; a roster littered with aging veterans plummeted back to the middle of the pack a season later and Dwyane Wade is about the only remaining reminder of their lightning-in-a-bottle season.

Rasheed Wallace

Boston's big offseason acquisition, Rasheed Wallace, is fitting in with his new teammates as if he's been here for years..
Brian Babineau/NBAE/Getty

The Celtics may not be as precariously positioned as were the Heat, but they are similarly loaded with veterans, and if they learned anything about championships last year, it's that winning more than one title is an accomplishment for the ages. No one knows that better than Danny Ainge, a two-time champion in '84 and '86 who saw first hand in the late 1980s what an aging roster will do to a team's title aspirations and expectations.

In 2008, a spotlight in the Waltham practice facility marked the future home of the Celtics 17th banner. This season, there's an empty banner hanging in it's place, an even more obvious metaphor for motivation.

"We talked about this with the '08 banner, and we had the light shining on that spot, so we always knew what we were playing for," Ray Allen told reporters on Media Day. "Every day we walk into the gym that's what we're going to see up there, so were going to put some more lettering on that banner."

This team has the talent to hang another banner. Now they just have to fill in the blanks. With that in mind, the Celtics had to plug a few holes, as the sputtering end to 2009 revealed a lack of depth in the front court and scoring production in the second unit. Without Garnett, the team was undermanned and over-extended.

When the Basketball Operations department convened on draft night in the war room (the Red Auerbach Conference Room) at the team's downtown office, there was one name that kept coming up, and it wasn't second round pick Lester Hudson. Planning was already underway to put the full court press on Rasheed Wallace, luring the free agent big man to come off the bench for another chance at a ring.

Early in their Newport training camp, Wallace talked about how natural it felt to walk into the gym with KG and company, and it sounded like there'd be little if any turbulence with the transition. Wallace's presence, along with Glen Davis (who filled in for Garnett after his knee injury) and Marquis Daniels (another offseason find who took less to play for more with Boston after over a month of negotiations and machinations), gave the Celtics eight starter-quality guys and unmatched depth in the conference.

The team is marketing itself as "Reloaded", but shock and awe might be more accurate when describing the potential firepower on this roster. The second unit alone compares favorably with many starting fives in the NBA, and preseason results showed that the team as a whole could overwhelm their opponents when the spirit moved them.

But meaningless preseason victories had little sway over Celtics Nation, and even the arrival of Wallace and Daniels paled in comparison to the questions surrounding Garnett's return from offseason knee surgery.

While Garnett was especially candid about his health from Media Day through the preseason, Opening Night drew near and the questions pelted him from every angle, causing him to grow weary of the repetitive inquiries. Alley-oop dunks, dives to the floor and blocked shots be damned; the doubters weren't satisfied with the visual evidence and wanted to hear from the horse's mouth that he was ready for the derby that is the 82-game grind. And every expert analysis of the Celtics seemed to start the same way: "If they can stay healthy..."

While that same contingency applies to every team in the NBA, and every squad is presumably a year older than they were a season ago, the Celtics will apparently have to prove that they can stay healthy, especially in the first few weeks of the season. They may not have to rip off 19 straight wins or start 27-2 like they did last year, but they'll certainly have to make a statement in November before they'll silence the skeptics.

But that won't matter in the Celtics locker room. While they've claimed over the past few years that they didn't even know what their record was, or what history they might be making, they are well aware that they fell short of expectations last season, and they'll get their first opportunity to remind the NBA who they are tonight in Cleveland.