Why we care if C's lose Tony Allen

When the 2009-10 season began with Tony Allen sidelined by an ankle injury, it was met with shrugged shoulders. Just Tony being Tony.

In six injury-riddled seasons in Boston, Allen missed a total of 156 games, or a staggering 26 games per season. Only twice did he appear in 75 games or more in a campaign, while missing at least 28 games in each of his other four seasons.

So when Allen sat out the first 20 games this past season with a sore right ankle, an injury aggravated by his attempt to rush back from offseason surgery too quickly, it was met with familiar resignation.

Heck, some were still wondering why the Celtics even bothered re-signing Allen after the championship season in 2008, one in which he was finally healthy yet barely registered in the postseason (1.3 points over 4.3 minutes per game).

So why is the news that Allen, an unrestricted free agent this summer, is set to sign with the Memphis Grizzlies hitting so hard in Boston?

It's because, for the first time in his career, Allen looked like he was finally starting to get it. Over the final 62 games of the 2009-10 season and through the playoffs, Allen bought into his role as a defense-first guard whose sole focus was on slowing the opposition's best player, regardless if it was the likes of LeBron James or Kobe Bryant.

It was enough to make Allen an offseason priority for the Celtics. And once the team locked up both Paul Pierce and Ray Allen, it seemed like only a matter of time before Tony Allen was in the fold.

Celtics president of basketball operations Danny Ainge said Thursday at the summer league in Orlando that he had already engaged in conversations with Allen's camp, exploring the opportunity to bring back the reserve swingman as he reassembled the core of a team that came mere minutes from capturing Banner 18 last month.

Rumors even swirled late last week that Allen was set to re-sign with Boston. Then came the curveball Sunday: Allen was going to Memphis at a not-so-unreasonable fee of three years and $10 million.

At first blush, it's hard to understand why the Celtics might not have been willing to match such an offer. Maybe Boston didn't want to go that length based on Allen's injury history. Perhaps the Celtics are simply exploring other bench options and couldn't commit to Allen this early.

Regardless, it's bittersweet seeing Allen move on. Tantalizing at times but bafflingly frustrating at others, he could play stellar defense for the game's first 47 minutes, then fall for an upfake at the buzzer and cost his team a victory.

But Allen made great strides in changing his reputation this past season. He went to the altar of associate coach (and defensive guru) Tom Thibodeau and swore the only thing that mattered to him was helping the Celtics win.

True to his word, he expended almost every ounce of energy he had on the defensive end this season, allowing the offense -- once his focal point -- to come to him.

It seemed Allen had finally matured (even if he still loved screaming rap lyrics in the locker room, he at least did it while watching film and receiving treatment on his foot).

He finally got it (Allen often led the cheerleading on the sideline and was always into the game, just waiting for his opportunity to contribute on the floor).

And now he's gone.

It was quite the roller-coaster ride for Allen in Boston, but it stopped at about the same high as it started. A first-round pick (25th overall) in a 2004 draft that also netted Al Jefferson and Delonte West, Allen appeared in 77 games his rookie season and averaged 6.4 points, 2.9 rebounds and one steal per game. Those numbers are startlingly similar to his 2009-10 stats, when he appeared in 54 games and averaged 6.1 points, 2.7 rebounds, and 1.1 steals.

In between, he started to emerge as an explosive scorer, only to tear both the anterior cruciate and medial collateral ligaments in his knee attempting a post-whistle dunk Jan. 10, 2007. He made a fairly speedy recovery but seemed conflicted about whether he could still be a scorer despite his loss of explosion following the knee injury.

Ankle injuries have derailed him at times the past two seasons. Allen missed 36 games in 2008-09 and was an afterthought in the postseason. His ankle acted up again in this year's playoffs but he played through the pain and shined defensively.

It is slightly condemning that Allen played just five minutes in Game 7 of the NBA Finals. It's worth noting, however, that Boston leaned heavily on its starters that game.

Here's why Allen's departure really hurts Boston: Already over the salary cap, the team could have used Bird Rights to re-sign their own veteran free agent. The only downside: Boston is already over the luxury threshold and would have to essentially pay his salary twice (once to Allen and once to the league, which forces teams to pay dollar for dollar on any payroll over $70 million).

Replacing Allen isn't as simple as signing another available body. Being over the cap and without any remaining exceptions, the Celtics are limited to offering the veteran minimum to obtain a player in his mold. It's unlikely they can net someone of his caliber with that to offer.

The Celtics do hold one intriguing option that leaves you wondering if there's a Plan B in place. Boston still has roster flexibility until Rasheed Wallace formally declares his retirement (or, less likely, returns for the 2010-11 season). Boston could trade Wallace to a team eager for cap relief and obtain a proven wing for up to the $6.3 million Wallace would have earned next season.

But Boston could also use some depth in the frontcourt, and if it was targeting that with the idea Allen would be back in the fold, his departure could throw a wrench in Boston's offseason plan.

It's the first bump in the road for the Celtics' otherwise smooth offseason travels, and it will be interesting to see how they get themselves back on track.

Chris Forsberg is the Celtics reporter for ESPNBoston.com. Follow him on Twitter.