For Nets fans, this season must feel like deja vu all over again. Since sometime during the Beatles heyday – or at least it seems that long – the team has had the same basic roster problem: three all-stars and no supporting cast.

It isn’t for lack of trying on management’s part. Team president Rod Thorn moved aggressively during the off-season to revamp the New Jersey bench. He brought in guard Jeff McInnis, forwards Marc Jackson and Lamond Murray, and pivotman Scott Padgett. It was all with an eye toward bolstering the team’s anemic offensive production from the reserves.

The Nets also used their first-round draft pick on Antoine Wright, a 6-foot-7 swingman from Texas A&M.It all looked great on paper, but three quarters of the way through the season, it’s clear the moves didn’t work. The Nets are still only as good as their starting lineup.

Using Player Efficiency Rating (PER), John Hollinger’s metric that accounts for a player’s production on a per minute basis, it’s easy to see the gaping chasm between the Nets starters and reserves.

The starting lineup is even stronger when one considers that Nenad Krstic is a second-year player who is developing quickly and that Jason Collins is that rare player who is ill-served by this statistic. Collins is a master of doing all the things that are not easily quantifiable, though this season he has played through an injury.

The bench, beyond Padgett, is clearly the problem. Most championship contenders have five regular players in double PER digits. The Nets only other double digit PER man is Lamond Murray, and he rarely plays defense and thus rarely gets off the pine. Given that the reserves play between and quarter and a third of all available minutes, a steep drop-off can be a disaster.

On Sunday night the Nets’ starters built a 19-point third quarter lead in Oklahoma City only to watch the bench nearly fritter it all away before coming back to restore order and finish a 95-84 win.

During the off-season, the reserve players looked like a solid group of savvy veterans, but in fact, with the exception of Wright, the new acquisitions are a little too veteran. Too many players on the Nets bench are on the wrong side of 30 to be effective NBA players. McInnis, who was lost for the season in January with torn knee cartilage, is 31, Murray is 33, Marc Jackson, who was traded last month, is 31, Cliff Robinson is 39, and Jacques Vaughan is 31. The only vets with upside are the 22-year-old Planinic and recently acquired Bostjan Nachbar, 25.

Topping this mess is the fact that Wright has been a major disappointment. The Nets drafted him hoping for immediate perimeter offense. Instead, the swingman who was taken ahead of Indiana’s Danny Granger, and (ahem!) the Knicks’ David Lee and Nate Robinson, has shot a miserable 37% from the floor and hit just one of his one of his 13 attempts from behind the arc.

It’s not a rosy picture, but the Nets have survived the worst of this situation already. As the playoff push nears, teams will shorten their benches somewhat, then shorten it again in the playoffs, when many teams use only seven or eight players. That means the Nets won’t have to worry about teams overwhelming their weak reserves.

Presuming the Nets hold off Philadelphia for the Atlantic Division title, they’ll be the hip choice to lose in the first round. In all likelihood, they’ll knock off the sixth seed and end the season with a series loss to the Heat – just like last year.

The subsequent off-season will be another opportunity for the Nets to build a solid set of reserves. In addition to their own first-round pick, they have the Clippers’ pick thanks to the Kerry Kittles trade, which looked like a fire sale at the time and now looks like a stroke of genius.

The draft is low on LeBrons at the top, but projects to be rich in complementary players in the middle- and late-stages of the first round, which is where the Nets figure to be picking. Along with the two picks, they could begin next season with three rookies if they import center Mile Ilic (their second-round pick from last year), who is still playing in Europe. The team will also possess its mid-level exception and several smaller veteran minimum slots if Robinson hangs it up and they buy out McInnis.

Another solid element of Thorn’s planning last summer was that if it didn’t work, the Nets wouldn’t be stuck forever with bad contracts (Isiah, please take note).

But that doesn’t mean Thorn won’t have to approach this summer with some serious urgency. Carter, Kidd, and Jefferson comprise one of the most formidable trios in the NBA, but time is running out. Kidd is 33 and though good rebounding guards age better than most, 33 is pretty old for any perimeter player. Carter has only two years left on his contract and it may be prudent to let Vinsanity walk after 2007-08 season rather than overpay him for the decline phase of his career.

This summer probably marks the last chance for this edition of the team to move into the ranks of the elite (both Finals appearances came in years when the Eastern Conference was a second class citizen of the NBA).Thorn’s energy last off-season was encouraging, but his track record isn’t. If he doesn’t improve his team, then this edition of the Nets will go down among the dozens of NBA teams that were very good for a long time without ever really being great.

mjohnson@nysun.com