Before we deal with whom the Nets should take with their pick in Thursday night’s NBA draft, it’s prudent to wonder if it will matter. Great drafting built the core of the Nets Finals teams in 2002 and 2003, but things have gone south since then. It’s not as if the scouting is bad; something else is amiss.

Let’s look at the Nets’ picks since the Spurs sent them home in the finals four summers ago.

This should make the problem fairly obvious. The Nets’ drafting isn’t the issue; the talent development is. Korver and Khryapa have been the most productive Nets draft picks in the last four years (which is damning evidence in and of itself since neither player often finds his name and the word productive in the same sentence), and those two were nurtured by the 76ers and Trail Blazers, respectively.

Meanwhile, the Nets’ draft picks have been one bust after another. Planinic is back in Europe after three stateside seasons where he neither took care of the ball nor shot it well. Despite 23 starts last season, Wright is closer to investigating graduate programs than he is being an effective NBA player. He can’t shoot and makes too many turnovers. Ilic played garbage time in five games this season before he disappeared into a witness protection program.

It’s too early to call the 2006 draft picks busts, but the most heralded of the trio, Marcus Williams, isn’t off to a promising start. Williams, a potential lottery pick who fell to the Nets at no. 22 last season, was given a rotation slot in training camp, then spent 82 games doing his best to give it back. I know this sounds like a broken record, but he couldn’t shoot and committed too many turnovers.

Oh yeah, the two main assets about Khryapa, when given substantial playing time, and Korver is that they shoot better than the league average and don’t turn over the ball.

Anyway, Adams and Boone have both shown substantial promise. Both forwards shot well, and Boone was a force inside. He averaged 15.2 points and 10.5 boards per 40 minutes of action last season. Maybe he ignored all the advice that brought so many Nets rookies down.

I should note that the failure to find an impact player isn’t entirely a result of the Nets’ low draft position. Across the river, the Knicks have taken David Lee, Trevor Ariza, and Nate Robinson with picks lower than any Nets first rounder. Put those guys on the bench behind the Nets starters, and we might be talking about a ramp up for a title run.

With a draft slot a little south of lotteryville, the Nets are likely to get a quality player who fell at the last minute. Before we consider the players, what do they need? In a word, the Nets chief priority should be a good defender.

The Nets, a stellar defensive team throughout the Lawrence Frank era, fell to 13th in Defensive Efficiency (points allowed per 100 possessions) last season after finishing third in 2005-06. The Nets have done their due diligence bringing in a wide variety of players who could fall to them at no. 17.

With Mikki Moore likely to be resigned, and Nenad Krstic returning from a season-ending injury early on, I think the Nets interior presence is solid and will become much better if Boone continues to develop. They should focus the pick on a perimeter player, so that the offense doesn’t grind to a halt when guards Jason Kidd and Vince Carter or forward Richard Jefferson sits.

Point guard Daequan Cook, the freshmen shooting guard from Ohio State; Jarvaris Crittenton, the freshmen point guard from Georgia Tech, and Marco Belinelli, the 20-year-old shooting guard from Italy, have all impressed at the team’s sponsored workouts in Tarrytown, N.Y. While an athletic wing player always sparks the dreamer in every hoops fan, I think the Nets should be more pragmatic in their selection and take Acie Law, the senior point guard from Texas A&M. Law isn’t as sexy a choice as some players that will be available to the Nets, but he is NBA ready (and yes, he can shoot well and take care of the ball).

The Nets have done an abysmal job at developing perimeter talent so taking a teenager who can play the point may lead to yet another draft day disappointment. Regardless of what happens with Vince Carter’s pending free agency, the Nets have a limited window of opportunity during Jason Kidd’s time here and taking a player who can step in when Kidd goes to the bench, would seem like a big gain.

But I don’t think the Nets will take him. They haven’t brought him for a workout. Instead, I think the Nets will select Georgia Tech small forward Thaddeus Young if he drops to no. 17 and spend the pick on Belinelli if not. The Nets have been one of the few Eastern Conference teams to enthusiastically invest in European players, and Belinelli, though a string bean (6-foot-6/190 pounds), has an NBA-caliber jump shot and solid ball handling skills.

No matter who they take on Thursday, the Nets face a summer filled with key negotiations with Carter and Moore. Let’s hope they don’t overlook their badly malfunctioning talent development system while they’re at it. It’s kept the Nets mired in mediocrity.

mjohnson@nysun.com