Even with an obvious hole at point guard, the Dallas Mavericks had been blitzing opponents with a gorgeous flowing offense on pace to be the most efficient in league history. They likely cannot score the ball any better.

And yet: They sacrificed a future first-round pick and three rotation players to fill that hole with a star in decline who can’t shoot from anywhere — including the free throw line. Dallas has predictably leaked everywhere on defense, and it’s tempting to spin the upgrade from Jameer Nelson to Rajon Rondo — excuse me, four-time All-Star Rajon Rondo — as the Mavs tightening things up at the point of attack.

Rondo is a long-armed disruptor who can team with Tyson Chandler to snuff out opposing pick-and-rolls. He has the defensive rebounding rate of a power forward, crucial for a Mavs team that ranks a sad 29th in that category. But Rondo hasn’t defended well on a consistent basis in years. His reputation on that end outstrips his current skill level. Dallas is introducing an unknown element into its pristine offensive ecosystem and banking on a defensive upgrade that recent history suggests Rondo cannot provide.

The Case Against the Trade

The cost is significant. The deal is riskier for the Mavs than for the Celtics, who found a cold market for a 28-year-old recovering from an ACL tear on an expiring contract. Brandan Wright has been massively important as Chandler’s understudy in the Mavs’ pick-and-roll alley-oop show. His ability to finish with dunks, floaters, and hooks frees Dirk Nowitzki to space the floor as a spot-up shooter and secondary option. Wright probably tops out as a neutral presence on defense, but he’s stiffened his post-up work and provides more rim protection today than he did two years ago.

Also, and this is kind of important, the Mavs have precisely zero other reliable backup big men. They must have a lead on someone, and early reports have linked them to Jermaine O’Neal, who lives in Dallas and is presumed ambulatory.

Jae Crowder has been a bit player this season, but he also represented the Mavs’ best hope at developing a wing who can both shoot 3s and defend. The first-round pick may well fall in the 20s, and god knows Dallas has whiffed on just about every shot it has taken down there. But it’s still valuable and represents a real get for Boston, considering that expiring contracts have netted very little in midseason trades under the collective bargaining agreement.

The Mavs offense lives on ball movement and spacing; Monta Ellis has thrived as the lead ball handler, but he’s also a killer passer, and the Mavs are at their best when they’re pinging the ball to shooters dotting the perimeter. Rondo is a non-shooter, and as a result, he has almost always had the ball in Boston.

The Mavs were quietly comfortable parting with Shawn Marion in the offseason because they were sick of watching the Matrix’s man clog the paint while he lurked in no-man’s-land along the baseline. That’s exactly where Rondo likes to hide when he doesn’t have the ball. And when he’s had it, at least in Boston, he has liked to dribble it — around one screen, then another, then under the hoop and around the other end. That would not jibe well with the Mavs’ sharing.

Rondo has never been the alpha dog on a good NBA offense. The C’s have scored at a worse rate with Rondo on the floor for three years running, and they were generally mediocre even at their championship peak. He’s shooting 41 percent this season and a laughable 12-of-36 from the foul line. His turnovers are through the roof, and a disturbing number of them have been unforced. Rondo has coughed up the ball on 32 percent of the pick-and-rolls he has finished this season, the worst rate among all 85 players who have run at least 50 such plays, per Synergy Sports. Dead stinking last.

Rondo has done wonders for Tyler Zeller’s field goal percentage, as ESPN.com’s Kevin Pelton points out, but his presence on the floor has made no consistent positive difference over the last three years for the shooting marks, per NBA.com, of Boston’s other core players — Jared Sullinger, Kelly Olynyk, Jeff Green, Avery Bradley.

There is very little evidence beyond inflated assist totals that the present-day version of Rondo is a helpful player — on either end. Dallas gave up real things for an overrated defender who wouldn’t seem able to improve upon an offense already challenging league records. Rondo will generate some steals and offensive rebounds, but the Mavs are already quite good at getting both of those things.

Sounds like a bum deal for Dallas, then, huh? It may end up one. But you can see how Dallas views it as a risk worth taking, and how Rondo could add up to more there than he has of late in Boston.

The Case for the Trade

We know Rondo has an extra gear when he gives a crap. The Mavs are betting that Playoff Rondo is still in there somewhere, waiting to be unleashed. “This will be a Chauncey Billups–to–Denver–level addition,” one league executive says. Playoff Rondo could make a dramatic impact on defense for Dallas as it navigates through Russell Westbrook, Damian Lillard, Tony Parker, Stephen Curry, and the rest. Even a semi-comatose Rondo contemplating his next Connect Four session is an upgrade on that end over Nelson, J.J. Barea, and Raymond Felton.

His size matters for a team with so many point guards. The Celtics already had Rondo guarding some wing players, which allowed them to sic Bradley on opposing point guards. Rondo has the length and tenacity for it; who can forget him going toe-to-toe with LeBron James for a few precious playoff possessions?

He can play next to Barea and Devin Harris, and the Rondo-Harris combination offers decent size on hybrid bench units — perhaps even with Ellis as the nominal small forward in super-small lineups.

The fit on offense will be awkward, and Dallas cannot reasonably expect to improve much overall on that end. The shooting downgrade from Nelson to Rondo will hurt. The Mavs withstood the loss of Jose Calderon’s shooting, but for all of their offensive brilliance, Dallas is a so-so shooting team beyond the transcendent Nowitzki. Can it absorb another downgrade? You never know which tap at the rock will be the one that breaks it apart.

But the Mavs are 0-5 against incumbent Western Conference playoff teams, and they’ve laid some stinky eggs on offense in those five losses. They are murdering the dregs and stalling out, at least in relative terms, against the teams they’ll need to beat to make a Finals run. Nelson can drain open 3s, but teams aren’t contorting their defenses in fear of his shooting. He can’t finish at the rim — he’s shooting just 38 percent near the basket, per Basketball-Reference.com — and he’s made fewer foul shots than Rondo.

He’s just not a dynamic player. He’s not a rim attacker. Rondo is a speed demon shooting better than 57 percent near the basket. Once in the paint, he has the dexterity and vision to find anyone, anywhere. None of the other Dallas point guards, including Nelson, is in Rondo’s universe as a passer.

Rondo has the potential to give Dallas another gear it appears to need against the best teams. He can’t shoot, but he’s a smart player, and the Mavs are wagering on their collective IQ here. Ellis was a chucking bust until Rick Carlisle partnered him with Nowitzki, and now Chandler, and freed him to attack the basket at will.

Rondo loves to hold the ball, but he’s obviously unselfish, and under Brad Stevens he’s shown that he’s happy to pepper the thing around to spot-up shooters stationed along the 3-point arc. He’s perfectly capable of bobbing around an Ellis-Chandler pick-and-roll, catching a kickout pass, and going right into a secondary driving action without pausing to pound the ball. The Rondo-Nowitzki pick-and-pop is going to kill people. Carlisle, Rondo, and the rest of this veteran cast will figure out how to integrate him without siphoning their pass-and-drive mojo.

There will be times when the Mavs feel a spacing crunch, but that issue can only be so serious as long as Nowitzki is on the floor. Great shooting from a big man is worth more than great shooting elsewhere, since Nowitzki drags an opposing big — a potential rim protector — away from the basket while setting a flurry of picks.

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Wright was valuable in Dallas, but the Mavs couldn’t protect the defensive glass when he was on the floor, and his trade value will never be higher than it is today. Carlisle rarely played Wright and Chandler together, so as good as Wright is, he was going to be a low-minutes guy in the postseason. A Chandler injury is a disaster now, with no viable backup, but it was going to be a disaster regardless.

We shouldn’t ignore the future here. The Mavs could have carved out cap space this summer, but only if they renounced Bird rights on Ellis and Chandler and (likely) let them walk in free agency. Cap room isn’t that valuable if it gets you worse versions of players you used to have. The future of this franchise was uncertain beyond Nowitzki and Chandler Parsons.

It’s still uncertain, but Dallas now has home-court advantage on three high-level free agents — the right to offer more money and larger annual raises than any rival bidder. That’s not a huge advantage when it comes to free agents earning below the maximum salary, and the Rondo of the last 20 months is not a max player. But every edge matters, including familiarity and comfort. The Mavs today have to fret much less about scrounging a so-so free-agency market for everyone’s leftovers.

They’ll need another big man, especially if Greg Smith proves unable to earn Carlisle’s trust, but the Mavs are taking a swing on the kind of talent they just weren’t going to be able to get this season in any other way.

What Does This Mean for Boston?

For the Celtics, this is a disappointing deal on the surface — but only on the surface. You can cherry-pick other recent deals for expiring and semi-expiring contracts that netted better return, but the circumstances are never equivalent. The Magic got more for Dwight Howard, but he’s Dwight Howard. Rajon Rondo is not Dwight Howard.

The Rockets got what will likely be a better first-round pick for Omer Asik. The Bulls got cap relief (Andrew Bynum) and multiple picks, including what could be a late lottery pick this June from the Kings, in the Luol Deng deal with the Cavaliers.

Those Cavaliers were desperate to make the playoffs, tossing bundles of picks all over the league for veterans who didn’t move the needle. New Orleans is desperate to make the playoffs now, and the Pelicans nabbed Asik in the summer — in time for training camp and the full season.

Boston was dealing Rondo in the middle of the season, giving any potential suitors much less time to integrate him. It didn’t have a trade partner with the right combination of sweaty “WE HAVE TO WIN NOW!” desperation and good trade assets. The Lakers can try to sign Rondo this summer, which is why they were planning to cap their offer at Steve Nash, the Houston first-round pick they got with Jeremy Lin (likely to be in the mid-20s), and a second-rounder, per sources familiar with the matter.

The Rockets could have dangled a potential lottery pick from New Orleans (the Asik pick), but they appear to not have done so, and they’d have needed a third team to make a deal with Boston. The wackadoo Kings didn’t pony up in the end, and there just aren’t many other teams with a need at point guard and any motivation to deal picks. Maybe the Knicks would have done a dumb Knicks thing had they already not done a dumb Knicks thing in dealing a first-round pick and two second-rounders for Andrea Bargnani. They’re also set to have big-time cap room this summer for Rondo’s free agency, and he would appear a bad fit for the triangle.

The market just wasn’t there. It’s easy to criticize Boston for waiting too long, and it was indeed asking two and even three first-rounders for Rondo over the last year or so, per multiple league sources. But the Celtics weren’t getting more than this in the end.

Rondo’s ACL tear in January 2013 was devastating in every way. Last season, 2013-14, was the year to trade Rondo if Boston was determined to do so. The Celtics were determined, but there was no getting max value as the league watched to see what Rondo looked like after his midseason return.

Trading Rondo in 2012-13, with three seasons to go before the expiration of his contract, would have been cutting bait way too early on a healthy star in his prime. Hell, Paul Pierce and Kevin Garnett were still on the team then; Boston was just a few months removed from taking Miami to Game 7 of the conference finals.

Trading Rondo now, a few months from the end of his contract, is too late for Boston to get a fat trade return. Rondo’s knee injury obliterated the sweet spot — the two-years-away trade Utah made with Deron Williams.

All things considered, Boston has done fairly well here. The Celtics convinced Dallas to protect the pick in both directions, per Yahoo’s Adrian Wojnarowski, so that the Mavs keep the pick in the 2015 draft if it falls within the top three (ha!) or between no. 15 and no. 30. That last part is key. Boston wants to maximize its chances of getting a decent pick, and it knows Dallas is picking in the 20s this season.

After 2015, the pick is only top-seven protected, so that if Dallas somehow blows free agency or otherwise dives into mediocrity, the Celtics could get a pick in the middle of the first round. That’s a solid return, considering that only one certain first-round pick changed hands over the last two trade deadlines combined.

The Celtics, in the meantime, get a free look at Wright, Crowder, and Nelson. Wright and Crowder are both set to be free agents this summer, though Crowder will be restricted. All three could net some return at the trade deadline. Wright and Crowder could be keepers at the right price. Wright provides a bit of rim protection, badly needed in Boston, and you can envision him slicing down the lane on pick-and-rolls as Sullinger and Olynyk spot up. (Kindly ignore the question of who might be dribbling the ball.) Crowder is a menace on defense who has improved his 3-point shot, especially from the corners. The Celtics also get a fat trade exception here, a nice carrot for later.

It’s not the bonanza Boston and its fans were expecting two years ago, but that kind of return became unrealistic almost the moment Rondo tore up his knee. It couldn’t risk Rondo for nothing, clearly didn’t want to give him the max, and realized after losing out on Kevin Love that Rondo likely no longer fit its rebuilding timetable.

Now Boston just needs to turn all of those draft picks, and all of that cap space, into a team — and with no other obvious star target on the horizon. Ask Orlando and Utah how hard that is.

It’s the end of an era in Boston. The starting lineup from the 2008 title team still hasn’t lost a playoff series. It never will. Those players are all gone now, and their quirky point guard is off to chase a ring elsewhere. He’s not likely to get it, but you have to admire the Mavs for going all in.