Why do NBA teams keep thinking Jeff Green is the missing piece?

Just before the trade deadline, the Clippers traded Lance Stephenson and a first-round pick to the Grizzlies for Jeff Green. It will be Green's third team in three years. Last year, Memphis traded Tayshaun Prince, Quincy Pondexter and a first-round pick to Boston. How did he get to Boston in the first place? The Celtics stunned the league and broke up a successful starting five to acquire him from the Thunder in 2011 for Kendrick Perkins.

Three front offices in the span of the last half-decade -- including two in the last 13 months alone -- convinced themselves that Green was the missing piece. The Grizzlies and Clippers gave up one of the most valuable assets in today's NBA --  a first-round pick -- to get him. The Celtics did one better, breaking up a beloved and championship-winning starting five to bring Green in. Why does this keep happening?

Teams talk themselves into Green because of his physical profile and skill set. He's a long, athletic 6'9 forward who has the ball-handling skills to play on the perimeter and the size to move up to power forward in small lineups. That is exactly the type of player that is in vogue today, because having lineup versatility is key. On paper, Green provides amazing lineup versatility.

Green also has the occasional game or stretch of games where he looks like a world-beater. During these glimpses when his fluidity as an athlete is on full display, his shot is falling and he uses his length on defense to make plays, he looks like an All-Star. In the five games leading up to the trade deadline, for example, he averaged 16 points, five rebounds, two assists and a steal for the Grizzlies. That's why GMs always fall in love with him. It's also why Charles Barkley can say Green could be "a perennial All-Star" with a straight face.

But those moments are few and far between. We now have an eight-season sample that shows Green isn't the star he sometimes seems to be. We know that he has always been extremely inconsistent, his numbers have often been hollow and he's never really figured out how to leverage his physical tools to help a team win over the long haul.

Green rebounds like a small forward. He's one of 24 players who are 6'8 or taller who pull down less than 15 percent of available defensive rebounds (minimum 1,000 minutes). Despite his length, he's not a good post defender because of his slender frame, ranking in the 29th percentile in the league. He offers very little in the way of rim protection as well, allowing opponents to shoot over 50 percent on the attempts he contests at the basket. He commits so many mental errors defending the pick and roll and guarding players in isolation.

If he were a full-time power forward, he would be comparable to Ryan Anderson and Ersan Ilyasova in those three categories. The difference is those other two players can shoot from outside well enough to draw their defender to the perimeter. Green is a career 34 percent shooter from beyond the arc, and is connecting on just 31 percent of his attempts this season.

That inability to hit three-pointers consistently puts him at a disadvantage when playing small forward, especially when he shares the court with two traditional big men like he did for most of his time in Memphis and he likely will now with the Clippers. He offers some shot creation, but he's always been inefficient, having eclipsed the league average true shooting percentage of 54 percent only once in his career.

At the end of the day, Green is a mediocre defensive player who is prone to inconsistency on both ends, doesn't do anything particularly well, can't excel at either forward position over the long haul and has traditionally been a drain on the court, with teams performing better when he's on the bench. He's also 29 years old now, not 24 like he was when the Celtics first talked themselves into thinking he could improve.

Expecting him to figure it all out and make a leap just isn't realistic. So why are teams still gambling on him?

The fact that he was selected fifth overall in the draft might have something to do with how he's perceived. After all, even Darko Milicic was given multiple chances to prove he was as disinterested about basketball as he seemed in his first few years in the league.

As mentioned, Green's physical profile and what it looks like he should be able to do surely play a part in general managers convincing themselves he could be a core player. By all accounts, Green is a smart guy who has overcome adversity. He's has never had off-court issues, and that matters.

Yet it's getting increasingly hard to justify the warped perception team after team after team has of his actual value. The evidence clearly shows he's just another guy. At best, he won't kill your team if his role is well defined and he's flanked by the right players. At worst, he'll float through games, teasing his club just enough to keep throwing him out there.

It really looked like the Grizzlies were going to be the last team to fool themselves into believing in Jeff Green as an impact player, as the Celtics and Thunder first did a long while ago. There were reports that Green had become a disruptive locker-room presence in Memphis. Usually, that's the last straw.

But at the last minute, the Clippers picked up the mantle. Doc Rivers coached Green in Boston, so he should know how frustrating he is as a player. Instead, Rivers rolled the dice again, and he might not be the last executive to do so. It wouldn't be surprising to see yet another franchise give Green another shot to prove he's as good as he seems, despite all the evidence that should deter them.

A team talking itself into Jeff Green is fast becoming an annual tradition.