Almost as vital to the Celtics' championship run — especially in the Finals vs. the Lakers — was Posey's knack for bagging important 3-pointers in clutch situations.

In other words, what Posey brought to the table has not been replaced, and is actually irreplaceable. Letting Posey get away will be the biggest reason for any letdown that the defending champs might suffer.

The age of the Celtics' superstars is still another worry. Ray Allen is 33, Paul Pierce will turn 32 during training camp, and Kevin Garnett will be 33 while the playoffs are in full swing.

Of these, Allen is the most vulnerable. With his various injuries and post-surgical miseries, he's missed a total of 35 games over the past two seasons. Also, for most of the playoffs, Allen couldn't find the basket with a map. After blaming his shooting woes on Rajon Rondo's not delivering the ball to him at the right time and the right places, Allen did recover his stroke in the last few games of the championship series. The Celtics will need much more consistency from Allen to once again win the last game of the upcoming season.

There are two problems that typically plague aging players: Being increasingly susceptible to injuries, and taking much longer to thoroughly heal and get back into action. Any lengthy down-time suffered by Allen, Pierce or Garnett would be devastating — especially with Posey not on the bench to fill the gaps.

There are also several reasons why the previous six NBA champs (Lakers, Spurs, Pistons, Spurs, Heat and Spurs) failed to repeat.

Given all of the possible pitfalls, Danny Ainge's offseason moves have been seriously inept.

Even when Darius Miles was at the top of his game, his defense was pitiful, his jumper was shaky, his game was marshmallow-soft and he was a total jerk.

The signing of Patrick O'Bryant to back up Kendrick Perkins provides little more than a sizeable warm body.

Unless Gabe Pruitt's game undergoes a stupendous improvement, or rookie J.R. Giddens turns out to be a prodigious talent — and considering that both Tony Allen and Eddie House are really 2-guards — the Celtics have no serviceable backup at the point.

None of the above is meant to predict an empty season for the Celtics. Rather, the intent is to roll out the reasons why a repeat is fraught with peril. After all, they're still the champs until somebody beats them.

Or, as is more likely, they beat themselves.