The Celtics took a long time to settle into roles.

When the Celtics started this season, Rasheed Wallace was a three-point shooter to spread the floor.  Glen Davis was a midrange jump-shooter.  Kevin Garnett was a superstar.  Rajon Rondo was secondary to the Big Three.  Marquis Daniels was the backup point guard.

Funny how much things change over the course of a season.

Here’s a look at the players who have seen their roles change the most from the beginning of the season until now (I only chose players who have been in a Celtics uniform all season long).

Kevin Garnett

Perhaps no other Celtic has been forced to change his game so drastically.  Garnett didn’t have to adapt to the rest of his team; rather, he’s had to adjust to an aging and deteriorating body that won’t let him make the plays he used to.

At first, Garnett’s metamorphosis was painful.  He allowed Rashard Lewis to blow right by him for a game-winning bucket; Kris Humphries to drive around him like he was standing in quicksand; and Al Harrington to repeatedly treat him like he was a jayvee scrub.  He missed dunks, and at times looked like he should be headed for retirement rather than the NBA playoffs.

As the season has gone on, though, Garnett has gradually become more and more comfortable with his now-limited physical gifts.  The game no longer comes as easy as it once did, and he will never again contend to win an MVP award, but Garnett has settled into his role as a defensive stopper and come to terms with his limitations.  He’s starting to make a real difference on both ends, but he’s just doing it in different ways than we’ve become accustomed to.

Rasheed Wallace

Over the latter part of his career, Rasheed has pretended to be Steve Kerr with a temper.  Sheed loves camping out at the three-point arc and firing threes until his shoulder becomes sore, but his ice-cold shooting this season (28.2% from deep) has alerted even Sheed that he needs to focus more of his work in the paint.  As A.Sherrod Blakely noted in his column today, Sheed has taken only 1.83 three-pointers per game this month.  That’s still about, oh, 1.83 too many, but far less than the nearly 5 attempts per game he was averaging at the All-Star break.  With Sheed finally heading down low more often, the Celtics are a better team.

Glen Davis

Big Baby started off his career as an energy man.  Last year he evolved into a pick-and-pop, midrange-game kind of player.  Now, he’s back to bringing energy, crashing the glass, and making a living in the paint.  While his new — yet old — self tends to highlight his weakness at getting shots up in traffic (get that crap out of here, Glen!), Davis is supplying the Celtics with a needed jolt of adrenaline every time he steps on the court.

Marquis Daniels

Daniels was the backup point guard to begin the season, as the Celtics decided not to sign a true point guard behind Rajon Rondo.  Now, the Celtics still don’t have a true point guard, but Nate Robinson has become the backup PG du joure.  Daniels has shifted back to his natural position on the wing, but for some reason the Celtics haven’t gotten a lot out of him.  I still like Daniels’ basketball IQ, but he tends to go David Blaine a lot and simply disappear.  In 10 minutes against Dallas on Saturday, ‘Quis somehow registered 0 points, 0 assists, 0 rebounds, 0 steals, and 0 blocks.  He DID, though, have a turnover and a personal foul as proof that he actually did enter the game.

Rajon Rondo

It’s not so much that Rondo’s role has evolved over the course of this season, but rather how much he has evolved from last season.  Last year, Rondo was superb at times (see: Chicago series) but didn’t necessarily bring his ‘A’ game every night.  The Celtics played their best when Rondo did, but couldn’t count on him to consistently provide them with his best efforts.

This year, everything’s been different.  Rondo has become the Celtics’ most consistent player, a constant threat to take over the game with either his passing, scoring, or defense.  I’d make the argument that Rondo has been the Celtics’ MVP this season, and I don’t think there would be too much dissent.  Even so, Rondo has had to change his role.

For awhile, Rondo was looked upon to score more frequently.  With his elderly teammates struggling to show the form of their youth, Rondo shouldered a larger scoring load than he would under ideal circumstances.  Now that his teammates have started to regain the bounce in their steps, Rondo has taken more of a backseat scoring-wise.  Still, he has performed admirably in his role as a pure point guard, and showed against Jason Kidd and the Mavericks he can still fill it up.

Kendrick Perkins

When KG was down with an injury, Perk was forced by necessity to become a low-post scorer, and he adjusted his game quite nicely to take on more of a scoring role.  Since KG’s return, though, Perk has struggled to revert to his role of little more than rebounding and defending.

“Sometimes, I let the offensive end dictate my defense,” Perk said a few days ago. “And that’s not a good thing.”

No, it’s not.  But Perk seems to have finally regained the mentality needed to do the dirty work, whether he’s scoring the basketball or not.

Paul Pierce

Pierce’s adjustments have been at once the most subtle and overtly obvious.  I know that makes absolutely zero sense, so let me explain.  For awhile, Pierce wasn’t himself.  It was plain to see he wasn’t playing well, but hard to tell why.  On the surface, he seemed like the same guy.  He wasn’t hobbling around like Kevin Garnett, and he wasn’t half-assedly waving at players driving by him like Rasheed Wallace.

But he was off, way off. And he was for a long time.  But he’s back to looking like The Truth, and — after scoring at least 25 points in three consecutive games for only his third time in the Big Three era — it seems like only nagging injuries were keeping him back.  The injuries seemed to even affect Pierce’s confidence: Doc Rivers said he had to tell Pierce to be more aggressive for the first time ever, and Perk has also gone on the record about the Celtics needing an aggressive Pierce.

Both Pierce’s aggression and his play now seem to be back, and Pierce’s return to normalcy is one of the biggest reasons for the C’s recent surge.  Before the four-game win streak, David Berri took a look at the Celtics’ performance since the season’s midpoint and decided Pierce was most to blame for Boston’s struggles.  Now, it’s his play that has elevated them back into the contender conversation.  Pierce is back to attacking the basket, scoring easy hoops, and being his team’s fourth quarter go-to-guy.  Then again, I guess that’s what he was supposed to be doing all season long.  It isn’t so much that his role has changed, but the way he’s filling it certainly has.

After injuries and acquisitions marred a large chunk of the season and kept the Celtics from narrowly defining roles for each individual, each player is starting to fall into his own little niche.  It’s been a long time coming, but the Celtics finally look ready to prove themselves as an elite team.

It’s no coincidence that they’re starting to hit their groove as players become more comfortable with their own roles.