When Danny Ainge maneuvered and was able to piece the Big Three (or the Big 2 ½ as I like to call them) together prior to last season, there was talk about how he sacrificed the future for an opportunity to be relevant again.

Now that the C’s actually raised banner No. 17, there aren’t a whole lot of people questioning Ainge these days – and rightfully so.

Ainge jettisoned Al Jefferson, a pair of first-round picks and Ryan Gomes (I don’t count Sebastian Telfair or Gerald Green) on July 31, 2007 to land Kevin Garnett. The deal ranks right up there with Red Auerbach’s trade in which he sent Joe Barry Carroll to Golden State for Robert Parish and the rights to Kevin McHale.

Not only did the Celtics become instantly competitive, they won the NBA title last season and are in position to contend for another championship this year.

But C’s fans need to enjoy this while it lasts.

The window won’t stay open forever, maybe another three or four years. Ray Allen is 33, Garnett is 32 and Paul Pierce turned 31 last month.

Allen is replaceable after his contract runs out in a couple years and maybe Ainge can bring in a big-time shooter to take his place.

But there is no replacement for K.G. – or even Pierce for that matter.

Sure, Garnett is a warrior whose intensity suggests, on the surface, that he may never feel the effects of aging. However, NBA players just don’t continue to play at the highest level once they hit their mid 30’s. It’s beyond a rarity.

There’s not a single player among the NBA’s top 49 scorers older than 33. Father Time usually takes hold when you hit your mid-30’s and while some are reluctant to admit that fact, Allen (who is just 14 days younger than Allen Iverson for the distinction as the oldest player among the NBA’s scoring leaders) isn’t the player he used to be.

I’m not saying his career is over, but it’s clearly on the downswing. When he let it go from long distance in the past, the clear assumption was the shot would find the bottom of the net. Nowadays, he’s shooting 32 percent from beyond the arc – which doesn’t even rank in the top 75 players in the league.

Garnett’s play, while still at an All-Star caliber level, has also started to see his play decline. His scoring is at its lowest since his rookie year back in 1995-96 and his rebounding has also taken a significant dip.

The reality, whether anyone wants to hear it or not, is that while this team is still the odds-on favorite to defend its NBA title, the gap is closing. The young guys – such as the Atlanta Hawks and Portland Trail Blazers of the world – are making strides while the Celtics will eventually begin to show the signs of an aging team.

Ainge has done a nice job putting some nice pieces around Pierce, Garnett and Allen.

However, let’s not try and suggest that Rajon Rondo will someday turn into Steve Nash and be the cornerstone of the franchise. He’s a perfect fit to go alongside the Big Whatever-You-Wanna-Call ‘em because of his ability to push the ball, make quality decisions and defend.

But what happens when teams play him straight-up and don’t have to focus all their attention on the other three guys?  Rondo becomes the average NBA point guard that he is.

And I don’t even want to hear about Kendrick Perkins being anything more than an average NBA center – and that’s at best. Sure, the guy is a solid defender – but he’s still more unpredictable than a Yo-Yo.

The Celtics won’t be drafting anywhere near the lottery in the next few years and Ainge doesn’t exactly have a Jefferson to dangle in front of teams to try and land another big-time player.

That means he’ll have to ride it out with Allen until his contract expires at the conclusion of the 2010 campaign and then start the bidding war to try and convince one of the big free agents to come to Boston.

Boy, it would be nice to see LeBron or D-Wade – or even Chris Bosh in the C’s uniform.

But in all seriousness, why would LeBron James, Dwyane Wade or Bosh want to come to Boston to play with a couple of aging vets well beyond their prime?

It’s not going to happen.

So, when you start to digest all that turkey, give thanks for all the success the local teams – including the Celtics – are enjoying these days.

Because it won’t last forever.

TOP 10 ROOKIES

1. Derrick Rose, Chicago – The athletic point guard is averaging 19 points and 5.7 assists and is logging plenty of playing time.

2. O.J. Mayo, Memphis – I’m not the biggest fan, but he’s extremely talented. Mayo is averaging 20.6 points, 4.6 rebounds and 2.3 assists.

3. Michael Beasley, Miami – The skilled forward is putting up 14.8 points and 5.5 boards in 30 minutes per game.

4. D.J. Augustin, Charlotte – The former Texas Longhorn know how to play and he’s made a quick adjustment, averaging 12.5 points and 4.3 assists so far this season.

5. Luc Mbah a Moute, Milwaukee – Everyone questioned his decision to leave UCLA early, but it’s paid off. He’s averaging 9.8 points and 7.6 boards, which leads all rookies, per contest.

6. Anthony Morrow, Golden State – An undrafted free agent, the 6-foot-5 former Georgia Tech standout is a dead-eye shooter and is averaging 13 points while shooting 56 percent from long range in eight games.

7. Greg Oden, Portland – Not your typical rookie after missing all of last season, but the 7-footer still qualified. He’s had three double-doubles in nine games and is slowly coming along (8.3 ppg, 6.8 rpg, 1.7 bpg).

8. Brook Lopez, New Jersey – The skilled big man is averaging 9.3 points, 6.9 rebounds and 1.4 blocks for the Nets.

9. Jason Thompson, Sacramento – He’s a terrific athlete at 6-foot-10 and fits well into the Kings style. The former Rider star is putting up 11.4 points and 7 boards a game.

10. Marc Gasol, Memphis – Pau’s little brother is averaging a near double-double with 12 points and 7.2 boards for the Grizzlies.

Jeff Goodman is a senior basketball writer for FOXSports.com.