Last season, 35-year-old Ray Allen played 36 minutes a night in 80 games and didn’t miss any time because of injury. He shot a career-high from the floor (49 percent) and 3-point range (44 percent) and was once again an All-Star after a one-year absence.

Allen’s season was incredibly efficient. His effective field goal percentage, which is weighted to factor in 3-pointers, was also the highest of his career and ranked percentage points behind Arron Afflalo among guards who played more than 20 minutes a night. He also maintained his other numbers in rebounds and assists. (Oddly, Allen’s free throw shooting dipped to .881 percent, his “lowest” mark since the 2002 season.) 

To put it simply, Allen was as healthy and productive as he’s been in his four years with the Celtics. As expected, Allen is coming back to the Celtics after he decided to exercise his option for the final year of his contract that will pay him $10 million.

“I don’t have any plans to go anywhere else,” Allen said after the Celtics were eliminated in Miami.

Still, there was a question as to whether the Celtics would work out a longer extension with Allen or whether he would simply sign on for one more season. That was Allen’s call and his decision benefits both sides.

WHY IT’S GOOD FOR ALLEN

The last time he was in the final season of a contract, Allen's name was bandied about in trade rumors throughout the winter of 2010. He has always maintained that the rumors didn’t bother him but his shooting percentage improved noticeably immediately after the trade deadline had passed.

The downside for Allen is his affordable contract makes him an obvious trade piece if Danny Ainge decides to remake the team. But the key for Allen has been flexibility. The rumors are part of the trade-off.

This is also not a case of an aging veteran signing on for one more year. Allen believes, as do the Celtics, that he has more basketball in him. An obvious comparison is Reggie Miller who held the record for most career 3-pointers until Allen broke it last January. Like Miller, Allen relies on spacing and screens to get free for shots, and like Miller, Allen has aged particularly well.

The vast majority of perimeter players suffer a sudden and steep decline in their mid-30s, but Miller continued to play major minutes through the age of 36 and then remained an efficient shooter through the last three years of his career when his playing time was gradually reduced. That’s the same career path that Allen has been on the last few seasons.

By not signing an extension and coming back for one more season, Allen will be able to pick and choose where he wants to finish his career. He had interest last summer from several contenders but chose to remain in Boston. If the aging Celtics are unable to stay in contention beyond next season, Allen could sign on somewhere else for another run at a title.

Of course, Allen could also choose to stay and he is in a perfect offense to utilize his skills. While Paul Pierce has received deserved credit for transforming his game once Allen and Garnett arrived, Allen has also adjusted.

In his last season with the Sonics, Allen used almost 30 percent of the team’s possessions. In Boston, that number has dropped to an even 20 percent, which is in keeping with the Celtics' ball movement and team approach to offense. That dispersal of offensive responsibilities has been a key component of extending the shelf life of the Big Three, as well as their embrace of the strategy.

By exercising his option, Allen is assured of remaining in a good situation while still keeping his flexibility in what will likely be a transition phase.

WHY IT’S GOOD FOR THE CELTICS

In the warped economics of the NBA in which true superstars are actually underpaid and mid-level players absorb a huge chunk of salaries, Allen’s salary stands about as close to fair-market value as you can find. It also would have been incredibly difficult for the capped-out Celtics to replace Allen.

His return means that the Celtics have about $65 million committed to six players next season: Rajon Rondo, Jermaine O’Neal, Avery Bradley, Pierce, Garnett and Allen. There are many things that might change once the league and union work out a new collective-bargaining agreement (the current one will expire on July 1), but for now what you see with the Celtics is what you’re going to get. Unless Ainge pulls off a significant summer deal, Pierce, Garnett and Allen will come back for one more shot with a few tweaks to the rest of the roster.

The key for the Celtics is the summer of 2012 when Garnett, O’Neal and Allen will all be free agents, which will clear more than $37 million off the books. The Celtics have been making – or not making – moves with an eye on 2012 since last summer when Ainge decided to not offer Tony Allen a three-year contract last summer at the outset of free agency. 

This leaves Ainge with a handful of options. He can either pull off a big deal this summer or at the trade deadline, or he can simply play it out with a team that won 56 games and then start over in 2012 with a healthier cap situation.

Allen’s decision to use his option keeps both possibilities alive and brings back a necessary piece for next season.