Mavericks breaking all the rules

You never trade your best player (or second-best player) for anyone other than the other team's best player (or second-best player). But for the second time in three months, the Dallas Mavericks have gotten a team to violate that sacred NBA principle.

By getting Antoine Walker and Tony Delk from Boston for Raef LaFrentz, Jiri Welsch, Chris Mills and a future No. 1 pick, the Mavs, essentially, traded Nick Van Exel and LaFrentz -- and their $100 million in combined contracts -- for Antawn Jamison, Walker and Tony Delk, which I would call a steal. (Once and for all, let us retire the notion that there are untradeable players in the L.)

The Mavs-Celtics part of that deal allowed Mark Cuban to erase his own mistake ($69 million for LaFrentz last year) and re-direct that money to Steve Nash, who can opt out of his deal -- a modest $5.9 million on the cap -- after this season. Dallas would have had to cough up for Nash anyway, but now the Mavs can pay him without taking a prohibitive luxury tax hit down the road.

On the court, yes, Dallas has a lot of forwards -- Dirk Nowitzki, Jamison, Walker, Danny Fortson and Eduardo Najera. But if there's anyone who loves throwing guys out on the floor without a thought to their normal position, it's Nellie. If the Mavs zone it up more this season, they could force you to face these five at the other end: Walker at point forward, Nash (or Delk) at the two, Michael Finley at the three, Jamison at the four -- and Dirk Diggler in the middle! What center do you know that's going to chase him around screens? (And the Mavs have to wonder if Fortson is going to be able to stay on the floor this season.)

Nellie loved to go small with Van Exel and Nash together in the backcourt last season. Travis Best isn't that kind of combo guard. But now, Delk can step into the Nick at Nite role alongside Nash (or Best). Van Exel had a great postseason; he took out the Kings almost by himself. But isn't it reasonable to assume that he can't play much better? For much longer? At best, he was Dallas' third-best last season, and it is Finley who remains the team's heart and soul -- and its best conduit to Walker, a fellow Chicagoan and good friend.

There were nights when LaFrentz rebounded and blocked shots, but there were too many more nights when he just didn't deliver. Nellie tried yelling, he tried kid gloves, he tried ignoring, but he couldn't get consistent play out of him. Nor did LaFrentz play well next to Shawn Bradley, and we know Bradley isn't going anywhere.

Is Dallas giving up defense for more offense? Yeah, and what are you going to do about it? That's what the Mavs do. And if Cuban has proven one thing since taking over, it's that he can find somebody that will take his bad contracts. So if Jamison doesn't pan out, he'll be sent packing somewhere, and Dallas will re-sign Walker, who has an opt-out at season's end.

I just like Walker more than others, I suspect.

Here's what the Celtics are likely thinking: They had neither the inclination nor the (pre-tax) dollars to give Walker the big extension he was looking for (as I've told you both in print and on TV, Danny Ainge's first meeting over the summer with 'Toine was a disaster, with Ainge telling Walker he didn't think much of his game and Walker telling associates he was definitely out of Beantown at year's end). So Walker was on borrowed time from the time camp began, although he dropped close to 20 pounds over the summer.

The C's made summertime calls to the Blazers and Clippers (I thought they'd get something done with the Pacers, who have always coveted Walker), but when they couldn't lay a glove on Rasheed Wallace or Elton Brand, they turned to Dallas. In the East, I suppose LaFrentz is more than a credible center -- when he was in Denver, a half-dozen Eastern teams were salivating for his services -- whose perimeter skills should open up driving lanes for Paul Pierce. In the East, his shot-blocking skills may be more in play -- especially if Boston's team D gets back to where it was two years ago. And Boston believes that Walker's scoring can be made up by increased contributions across the board, from camp surprise Mike James (signed after coach Jim O'Brien and Ainge got the Alonzo Mourning seal of approval for his ex-Heatmate) to LaFrentz to Eric Williams and rookie Marcus Banks.

To me, though, trading Walker puts the spotlight square on Vin Baker. He's dropped 30 pounds, and he's showing some of the low-post skills he had in the past. He's been excelling in outlet passing drills and overall, he's had such a strong preseason that he's got a new nickname -- "Flash," as in flashbacks. Now, though, Baker's not just a good camp story, he's a necessity. With Walker gone, Baker has to be the Celtic who gets in the post, who hits the glass, who gets to the foul line along with Pierce.

I know that the Celtics view this as a potential four-for-one deal. They think Welsch has combo guard skills, but so did the Mavs, and so did the Warriors. The first-round pick, probably late in the round, will produce a low-salaried player who can be developed during the next five years. And the short-term savings of LaFrentz's deal over Walker's could allow Boston to get in the market for a mid-level exception free agent next summer. All true, but ...

You don't trade your biggest assets for more, smaller assets, no matter how many of them come back to you. Is Walker overrated? A ball hog? A turnover machine? All three may be true. But he was still an All-Star, and one of the key reasons the C's had gotten back to being a playoff team. Ainge needed to do better than this.

David Aldridge, who covers the NBA for ESPN, is a regular contributor to ESPN.com.