Many projected the departures of Kevin Garnett, Ray Allen, Paul Pierce (via trade) and head coach Doc Rivers.
But the core of the Celtics chose to stay besides Allen, who bolted to arch nemesis Miami.
Allen's departure will hurt, but he was the most expendable of their "core four": Allen, Garnett, Pierce and Rajon Rondo.
What's more, the Celtics added an array of weapons in the offseason and now enter the upcoming season with more depth at seemingly every position.
As a result, this era of Celtics basketball has not yet closed. In fact, if these Celtics can remain healthy, they stand as good of chance as anyone at dethroning Miami and capturing the NBA crown.
Let's examine their roster makeup for next season. Their identity will remain the same, but some new faces have altered the look of the depth chart.
If people were in doubt concerning Rajon Rondo being an elite point guard, then they no longer should be. Rondo mesmerized the NBA landscape with his performance in last year's playoffs, continuing to take his game to new levels and play with an unrivaled tenacity.
In the postseason, Rondo averaged 17.3 points per game, 11.9 assists per game, 6.7 rebounds per game and 2.4 steals per game.
Needless to say, he was playing as good of ball as anyone.
Interestingly, when this Celtics era began around five years ago, Rondo was the youngster along for the ride with three future Hall of Famers. Now it's his show. This team will follow after Rondo, and with the way he continues to progress, success is in store for the Celtics.
Newcomer Jason Terry can play either guard spot. It's not like his role will be limited to playing spot minutes when Rondo is out of the game.
Quite frankly, Rondo won't be out of the game very often, so the majority of Terry's minutes will come playing alongside Rondo at the two-guard spot.
Whatever the case, Terry will adapt and find his niche. He's a proven player and winner (integral member of the Dallas Mavericks' 2011 championship team), and he helps fill the void left by Ray Allen.
Terry actually brings more to the table than Allen. At Allen's old age, he had mainly just become a stand still three-point shooter. Terry can do this, but he still has the ability to put the ball on the floor and create.
He's quite a weapon for the Celtics to now have coming off their bench and could be the missing link that gets them back to the Finals.
Courtney Lee is another new addition who will likely be inserted into the starting lineup immediately. However, this is primarily because Avery Bradley underwent shoulder surgery and will most likely not be ready at the season's outset.
No matter what, Lee is going to play considerable minutes for the Celtics this season and he brings plenty of versatility. He's a superb defender who should get lots of opportunities to defend Dwyane Wade.
Lee's also capable of knocking down the three ball and should get plenty of open looks playing with Rondo.
What's more, despite only being 26, he already possesses playoff experience after traveling to the NBA Finals with Orlando in 2009.
He's a very helpful addition, and whether he's starting or coming off the bench, he will be a key figure in Boston's rotation.
Bradley will very likely be the starter at some point this season, but after undergoing shoulder surgery, there is not optimism that he will be ready to start the season.
Because of this, he'll likely be coming off the bench upon his return. Boston fans will be very excited when Bradley does return to action. He was hurt prior to last season's playoff series with Miami, and avid Boston fans surely believe that a healthy Bradley could have equaled a trip to the Finals.
Bradley's an elite defender and showed this on a consistent basis last season. He also showed much more improvement on offense, averaging 15.1 points per game in the season's final month, with an astounding 54.5 percent rate from three-point rage.
He brings a lot to the table and don't be surprised if he takes over the starting shooting guard reins soon after his return.
"The Truth" continues to play at a high level and has yet to show major signs of rust.
He still figures to log major minutes, but since the Celtics will possess more depth this upcoming season, he may be able to find more time to rest.
For instance, the Celtics could go with a small backcourt lineup of Rondo, Terry and Lee at certain points of games. Or, they may use a healthy Jeff Green (see next slide) for extended periods of time.
Still, you can expect Pierce to remain a featured player and leader on this team. He should continue to lead the team in scoring, but their new additions should help take some pressure off his 34-year-old legs.
Jeff Green, acquired in 2011 from Oklahoma City when Kendrick Perkins was dealt, is expected to play next season without limitations. He missed all of last season after undergoing surgery for an aortic aneurysm.
When healthy, Green is an incredibly skilled player. At 6'9'' and with adept quickness, he has the ability to guard multiple positions.
He's yet another valiant weapon the Celtics will possess this upcoming year that they didn't have last season.
His presence means the Celtics have a remarkable array of options and different lineups to use. Quite frankly, the backups of Terry, Bradley and Green make for a second unit that could compete with many teams starting units.
This is exciting for Celtics fans, because the team suddenly possesses needed depth.
Brandon Bass emerged last year as Boston's starting power forward, and he figures to remain there. He's particularly valuable because of his ability to hit the mid-range jumper.
If Bass can perform how he did last year, then this season will once again be a success for the 27-year-old.
The Celtics did draft power forward Jared Sullinger, and if "Sully" shows flashes of quality play, then Bass's minutes could be limited.
However, the C's know what they're going to get from Bass, and it's a decent player who can score and rebound effectively. No matter what, he'll have a steady role for Boston throughout the season.
Jared Sullinger has major potential. Concerns regarding his back caused him to fall down the draft board, but the Celtics weren't going to pass him up.
So far, he's made some great first impressions in the NBA's summer league, and he figures to instantly get minutes for the C's once the season starts.
At this size (6'9'', 265 pounds), he's quite a body to move around. He will definitely have value on the boards and his offensive game should steadily develop.
And who knows? Perhaps "Sully" will be one of the draft's biggest steals and end up being a perfect compliment at the four-spot to Kevin Garnett.
KG returns to Beantown and will surely bring the same passion, intensity and charisma to every single game.
He's the heart and soul of this ball club and all his teammates feed off of what he brings. Expect him to continue to tally around 15 points per game and eight rebounds per game while anchoring a defense that plays with a great deal of pride.
Celtics fans love "The Big Ticket" and with a few more quality years, perhaps Garnett's number will soon be hanging from the TD Garden rafters.
Chris Wilcox missed the majority of last season with a heart ailment, but he returns and should see spot minutes at the center position.
However, he will have to battle for playing time with rookie Fab Melo, a 7'0'' rookie from Syracuse who has great upside on the defensive end.
No matter what, neither of these players should see significant minutes, but if an injury occurs, then they could be thrust into an integral role.
The Celtics have increased depth amongst their big men, and if Sullinger and Melo live up to the hype, then Boston could have some of the best frontcourt depth in the league.