If you’re looking for the free-agent move with the most long-reaching consequences for the NBA, it isn’t Elton Brand’s move to the Sixers, nor Baron Davis’s jumping to the Clippers, nor even James Posey’s defection from Boston to New Orleans.

In fact, it wasn’t even an NBA signing.

But the inking of guard Brandon Jennings by Pallacanestro Virtus Roma of the Italian League could end up having far-reaching consequences for both the NBA and college basketball, because he may prove to be the tip of a very large, powerful iceberg.

The 6-foot-2-inch Los Angeles native is thought by most to be the top point guard in this year’s college recruiting class, and had already committed to Arizona. But he hadn’t yet qualified academically (the NCAA still pursues the fiction that elite athletes are there to learn about isosceles triangles and not the triangle offense), and that got him thinking about other options.

Enter Sonny Vaccaro, the longtime shoe maven who had bristled about the NBA’s age-19 requirement. Lately, he’s taken to wondering aloud whether some high schooler would be willing to do an end-run around the system by playing a year in Europe and making some dough. Jennings heard Vaccaro and thought it sounded like a great idea, and a few months later, here we are at a watershed moment.

If Jennings’s stay in Europe doesn’t turn into a disaster, there’s going to be a lot more like him in coming years. Or even sooner. Top recruit Demar DeRozan, for instance, hasn’t qualified academically at USC and could follow in Jennings’s footsteps later this summer.

The temptations for both sides are simply too great to ignore much longer. For the American players, there’s an opportunity to earn money immediately, with Jennings looking to earn in the neighborhood of $300,000 for a year’s work in Italy and more if he decides to stick around longer.

For players from poor families in particular, this is overwhelmingly more palatable than a year earning no money. Even for those who aren’t, a year living in a furnished apartment in Rome sounds considerably better than sharing a college dorm room in Tucson, Ariz., with a total stranger.

And for the foreign teams, the temptations also run strong. Most overseas contracts include a “buyout” figure for the player to get out of it if an NBA team comes calling. By rule, NBA teams can only contribute $500,000 toward such a buyout; by convention, they almost always pay the whole thing to get a player they want.

Thus, it’s not hard to see the incentive for European teams on the financials alone: Pay $300,000 to a potential first-round pick for a year, put a $500,000 buyout stipulation into the contract, and then turn a $200,000 profit while also filling a position for a year.

It’s tempting on talent, too. Though the European leagues typically favor veteran players, their guards tend to be a notch below the big guys, and quick, athletic guards can have their way with most defenders at that level. So while a teenager like Jennings might need quite a bit of on-the-job training, he’d also be talented enough to contribute immediately and help European teams fill a hole in the roster. (Ironically, in this case Jennings’s Italian team had an opening because point guard Roko Ukic signed with the Toronto Raptors).

So the European teams can sign 18-year-old players for a year, give them some experience in a pro environment, and both sides make money in the process. Everybody wins.

But the NCAA and NBA both lose big. One reason the league put in the age-19 rule is that it loves the free publicity it gets from having its player perform at the NCAA level before turning pro. And while the NCAA has a built-in advantage from all the folks who will root for mighty alma mater come what may, losing marquee talent to Europe robs it of cachet with the casual fan — especially if most of the “one-and-done” players now going to the NCAA instead go to Europe.

They may lose even bigger than anyone thought, actually, because here’s the part that nobody’s thinking about: There’s no rule that a player has to turn 18 before signing in Europe.

Chew on that one for a second, and imagine the next LeBron-esque basketball prodigy as a 15-year-old being approached by a team in, say, Barcelona or Rome or Athens. Imagine the sales pitch:

“Son, you can play for free for the next four years, make huge bucks for some college without ever being a paid a cent, and finally jump to the NBA at age 19 … or you can play professionally right now, and we’ll pay you millions of dollars and help you take care of your family immediately, and when you aren’t playing your two games a week you can hang out at our topless Mediterranean beaches and sip a cappuccino. This isn’t 1950 — we have McDonald’s and iPods and malls just like the U.S., and half the people here speak English. And did I mention the topless beaches?”

In fact, if somebody with half a brain were running the European leagues as an entity instead of a series of loosely connected individual fiefdoms, they’d already be canvassing every All-American team in the country looking to establish themselves as a rival major league by inking a bunch of the best teenaged American players to long-term deals.

Fortunately, they aren’t — yet — so the NBA still has to time to recover from the damning effects of the age-19 rule. They need to scrap the rule entirely, and instead spend some time figuring out how to better integrate teenage players whose rights are owned by NBA teams into the pro game — most likely by making far more effective use of the D-League than most have done so far.

While the NBA would like to go back to the halcyon days when everybody played four years of college before entering the pros, the reality is that few players are willing to play for free for four years — or even one — just so they can read Proust and listen to obscure bands. The only thing that’s stopped them in the past is the presumption that the NBA and the NCAA are the only games in town.

Thus, Jennings’s realization that he had options in Europe has a very real chance of opening the floodgates for others in coming years. And that, in turn, has a very real chance of undoing a silly, if not downright un-American, age limit that never should have been enacted in the first place.

jhollinger@nysun.com