In the frenzied NBA summer of 2010, the Celtics very quietly had an active offseason. We’ll be counting down the 10 most important developments.

No. 9: Tony Allen leaves

Admit it: You never thought there would actually be a day when a Celtics roster didn’t include Tony Allen. Sure, there were summers when it didn’t look promising, but by August, T.A. would be back for another round.

Never did that seem more certain than this summer after Allen finally found a consistent role as a defensive stopper and excelled at it. He began to emerge late in the season when the bench rotation was an open question and then went toe-to-toe in the playoffs with Dwyane Wade, LeBron James and Kobe Bryant.

Bryant went so far as to call him “a great defender.” Kobe may have said it through gritted teeth, but he said it and there was ample evidence to back up that claim.

Defensive reputations are generally made in the playoffs when fans and media focus in a little more on the tiny ebbs and flows and the impact that a specialist can have on the game.

Getting a rep can also re-make a career. Based on his play, T.A. could look forward to getting some All-Defensive votes this season and national announcers would point out his stops a little more frequently.

After six seasons of countless injuries, false starts and failed experiments, things were finally looking up for Tony Allen. 

Funny thing though. As the playoffs wore on, and the questions about his career breakthrough kept coming with each round he began to get a little, well, defensive. “What you all don’t understand is,” he said during the Finals. “I just want to play.”

That chance to play was ultimately what drove him to accept a contract offer from Memphis. The feeling from various members of the Celtics organization is that their offer was generous financially, but that Allen simply felt that he would have more opportunities to play with the Grizzlies.

That’s certainly his right as a free agent, but his departure left the Celtics in something of a quandary. Namely, how would they replace Allen when they were over the cap and out of exceptions, leaving only the veteran’s minimum to offer free agents?

Rather than replace Allen specifically – and really, there are very few T.A.’s out there – Danny Ainge decided to buy in bulk. He re-signed Nate Robinson and Marquis Daniels, hardly a given when free agency started, and imported the likes of Von Wafer and Delonte West with partially-guaranteed deals.

Collectively those four will absorb Allen’s minutes and each player bring various superior offensive skills to the table – ballhandling, shooting, creating shots – but none offer the kind of defensive presence that Allen possesses. Allen’s absence will be felt more acutely when the Celtics play the Heat and they have to line up against Wade and James without their perimeter stopper.

Tony Allen played six seasons with the Celtics, almost unheard of for a role player off the bench, and in some ways this is the end of an era. Not a historically significant one perhaps, but an era nonetheless.

He was maddening at times, exhilarating at others and sometimes even both on the same play. But he was never dull and in the end all that patience finally paid off.  

Next: The remaking of the bench.