To those who see no purpose in center Gana Diop staying on the Charlotte Bobcats’ roster, think twice:

The Matt Carroll trade suggests otherwise.

Tuesday the Bobcats made the first trade of this NBA season. They sent Carroll to the New Orleans Hornets, getting back versatile forward Hakim Warrick. I don’t know how much Warrick will play here, but I guarantee it will be more than Carroll would have logged this season.

The Bobcats are overstocked at shooting guard. Gerald Henderson, Ben Gordon and Reggie Williams all were going to play ahead of Carroll. Meanwhile the Bobcats have searched for depth at power forward since the start of the free-agency period in July.

I don’t think the Hornets were interested in Carroll. As coach Monty Williams commented, Carroll has hardly played the past two seasons. But that wasn’t the point. Carroll represented a handy commodity in the NBA marketplace:

He’s an expiring contract. And so is Diop.

A team acquiring Carroll owes him no guaranteed money beyond this season. So by swapping Carroll’s $3.5 million salary for Warrick’s $4 million, the Hornets saved $500,000 without any long-term risk.

That’s where Diop comes in. He’s on the Bobcats’ books for about $7.4 million this season and nothing beyond that. Disappointing as Diop has been on the court, his salary slot might be quite attractive to teams looking to avoid the luxury tax in future seasons.

Say there’s a player with a multiseason contract on another roster. He isn’t helping that team but could help the Bobcats. The Bobcats could use Diop’s salary slot to trade for that player, just the way they moved Carroll to New Orleans. And both teams benefit.

Numerous Bobcats fans expressed surprise the Bobcats didn’t just waive Diop last summer under the amnesty clause, which would have cleared his contract from Charlotte’s salary cap. They would have done that had one of the Bobcats’ top free-agent targets – Kris Humphries or Antawn Jamison – agreed to sign here.

But in the absence of such a signing, there was no purpose in using the one-time amnesty provision on Diop. Why pay him not to play? And why eliminate the option of trading his contract later?

Finally, here’s a farewell to Carroll: Fans wondered why a guy who hardly ever played was named a co-captain. Those of us around the players all the time got it instantly.

Regardless of whether Carroll was still an NBA talent, he was the most respected player in that locker room. Carroll was at voluntary two-a-day workouts all summer with the Bobcats’ youngsters, which impressed the front office and new coaching staff greatly.

He was named a co-captain to codify his voice in the locker room. Management wanted Carroll’s professionalism and work habits to rub off on others. Hopefully that happened.

Five passing thoughts on the NBA and the Bobcats:

•  Most of you never heard of Memphis assistant GM Kenny Williamson – “Eggman’’ to his friends, and there were many – who died last week. Williamson was part of the Bobcats’ first front office, evaluating draft prospects. He was a street-smart guy who was never too busy to mentor younger scouts and aspiring coaches. You know that term “people person?” Eggman defined it. RIP.

•  Curious to see how new Los Angeles Lakers coach Mike D’Antoni adapts to his talent. D’Antoni leans toward an offense that has minimal post-ups, to open driving lanes for perimeter players. But when you have Dwight Howard and Pau Gasol, don’t you have to run some sets that optimize that size advantage in the lane? The good news for Lakers fans is D’Antoni is a master of pick-and-roll basketball.

•  It’s not a complete shock the New York Knicks are thriving this early in the season without Amare Stoudemire, and I don’t mean that as a knock on Stoudemire. It’s no secret Stoudemire and Carmelo Anthony are redundant in skill set. The elephant-in-the-room problem is they get in each other’s way on the court.

•  Granted, the Washington Wizards are without John Wall and Nene right now, and those are two big pieces. But the Wizards are bad. Really bad. After last season, I know really bad.

•  I’m glad the NBA took a tough stand on Sacramento Kings center Demarcus Cousins confronting San Antonio Spurs analyst Sean Elliott over comments Elliott made on the air. Cousins was suspended two games. Stalking an announcer because you don’t like what he said is ridiculous. If you must confront someone about words, at least do it with some civility.