By Brian Robb, CBS Boston

BOSTON (CBS) – The Celtics have been out of the postseason for more than a week now, but there are plenty of ex-Celtics roaming around the hardwood in the second-round of NBA Playoffs to keep us entertained.

Paul Pierce has been making headlines with his tremendous play and entertaining trolling with the Washington Wizards. Jeff Green has maintained his track record of being consistently inconsistent with his production on the Memphis Grizzlies.

The one man who got all the headlines on Tuesday night was old friend Tony Allen, who helped in the Grizzlies upset of the top-seeded Warriors on the road in Game 2 of the best-of-seven series.

Per usual, Allen did not do much damage on the offensive end, scoring a meager nine points in the 97-90 victory. However, his defense against sharpshooting guard Klay Thompson (6-of-15 from field, five turnovers) set the tone for a gritty Grizzlies win. Golden State shot just 23 percent from 3-point range, and turned the ball over a whopping 20 times, with Allen causing 20 percent of those miscues with his four steals.

All of this superb play led to some fun on-court trash talk by the wingman, who proudly boasted about his stellar defense while being mic’d up by TNT.

The performance even earned Allen a rare tweet from an admirer up in Boston, Celtics president of basketball operations Danny Ainge.

Ainge may still praise Allen’s game from afar, but watching the 33-year-old must be a little bittersweet for the longtime Celtics GM. For a man who prides himself on not letting any of his players walk away without getting value for them, Allen was one of the rare exceptions back in 2010.

Allen was a critical role player for Boston in the 2010 improbable run to the NBA Finals as he played the kind of defense in limited spurts on Kobe Bryant, LeBron James, and Vince Carter that we saw again last night against Thompson.

The Grizzlies stole away Allen from Boston in the summer of 2010 with a meager three-year $10 million contract, a deal that gave them the Celtics’ perimeter stopper in his prime.

The loss of Allen via free agency can’t be entirely blamed on Ainge. Memphis offered Allen a starting job, something Ainge couldn’t do with Paul Pierce and Ray Allen firmly entrenched in the starting five. Still, Boston likely would have been able to make up for reduced playing time with dollars, and Boston’s offer was not sufficient enough in Allen’s eyes to stay in Beantown.

Ainge never did replace Allen’s defense that offseason. He brought in Jermaine O’Neal on the mid-level exception, while relying on subpar players like Marquis Daniels and Von Wafer to play behind an aging Pierce and Allen. With both of those guys failing to provide sufficient minutes, Ainge was forced to deal away the beloved Kendrick Perkins for Jeff Green at the trade deadline… and we all know how that turned out.

Meanwhile, Allen has thrived in Memphis the past few seasons, blossoming into the elite defender we had all seen shades of in Boston.

In Avery Bradley and Marcus Smart, the Celtics have finally found a couple of players that show Allen’s defensive potential, but it’s undeniable that Allen’s presence in Boston during the tail end of the Big Three era would have likely brought a few more postseason wins.

As the 6-foot-5 wing continues to thrive in Memphis five years later, Celtics fans can only hope Ainge has learned his lesson as he attempts to move Boston into the next stage of their rebuild.

Brian Robb covers the Celtics for CBS Boston and contributes to NBA.com, among other media outlets. You can follow him on Twitter @CelticsHub.