Ever since Jason Kidd arrived, it’s been accepted in New Jersey that the Nets would contend for the Eastern Conference championship. In the past five years they’ve won it twice, lost in the second round two other times, and made the playoffs all five seasons. In four of those seasons, they lost to the eventual NBA champion, and it might have been five if Dwyane Wade hadn’t pulled that muscle in his rib cage. But for a brief blip between Kenyon Martin and Vince Carter, this has been one of the best teams in basketball.

But whether New Jersey will keep its prominent perch is an open question. Yes, most prognosticators have basically handed them the Atlantic Division crown, but New Jersey’s 49-win campaign last year disguised plenty of warts. For starters, they were lucky to get 49 based on my Expected Wins stat — they had the victory margin of a 46-win club. Looking ahead, Jason Kidd isn’t getting any younger, the big guys can’t rebound, and the bench is terrible. Throw in the distractions of Vince Carter’s free-agent year and Jason Collins’s battle of wounded knee, and the Nets’ status among the Eastern elite has never been more in doubt.

The touchiest issue in New Jersey these days is Carter’s impending free agency. Technically the Nets can sign Carter to an extension up until June 30, but the reality is he’ll probably hit the open market this summer. Carter has already said he doesn’t want to negotiate an extension during the season, and once the year ends, there’s really no point in him signing when he can play the open market risk-free. And there’s a real risk of flight here, because among other teams, Charlotte will have a huge cap opening, and Carter’s Carolina background could tempt him.

But that’s for this summer. The concern now is more how the free agency will affect Carter’s play during the season. With most players I wouldn’t really worry about it, but Carter isn’t most players. Anyone remember that mail-in job he pulled with the Raptors two years ago? The fact is he’s one of the few players who can turn his switch on and off as he pleases, and Nets fans have been fortunate to witness only the “on” position in his year-and-a-half in the swamp. Let’s hope he doesn’t start tanking games while he ponders real estate in the Carolinas.

Next up on the list of worries is that awful bench, one that they were fortunate wasn’t exposed more often: The big four of Kidd, Carter, Richard Jefferson, and Nenad Krstic missed a total of three games all season until they sat out the final two to rest for the playoffs. That’s an unusual run of health in the NBA, and one that isn’t likely to repeat itself.

So for the Nets to improve on last year’s showing, they’ll need a much better effort from the second unit. Probably the best hope for improvement is in the backcourt. A year ago Jacque Vaughn was the primary reserve, and while he’s a quality defender and a prince of a guy, he also can’t shoot to save his life. This year Vaughn is in San Antonio, and rookie Marcus Williams is filling the void.

Williams looked very good in preseason, showing a natural instinct for running the offense and shooting well enough that defenses won’t be tempted to leave him wide open … as they did with Vaughn. He isn’t nearly the defender that Vaughn was, however, and between the 33-year-old Kidd and Williams the Nets could have problems stopping dribble penetration this year.

The other good news comes in the form of Antoine Wright, who had a very solid preseason and appears to have cemented his status as the top wing reserve. Wright was brutally bad as a rookie, so hopefully what we witnessed was genuine improvement rather than the best three weeks of his life, because there’s really no Plan B here.

Veteran gunner Eddie House should also play a major role, although knee surgery will keep him out to start the season. He played for Phoenix last year and thrives in an improvised, uptempo system, so it will be interesting to see how he meshes with the more controlled in New Jersey. He’s also a lousy defender, which could get him in hot water with defense-first coach Lawrence Frank.

While the Nets can hang with anyone on the perimeter, the frontcourt is a much greater concern. I’m afraid Krstic’s development has been greatly exaggerated — he can score a little, yes, but at this point he’s basically a middle of the pack power forward. He just looks better on the Nets because they only have four guys who can score.

Meanwhile, Collins’s knee problems last year made him even more worthless offensively than usual, and Clifford Robinson turns 40 in December. None of these guys can rebound worth a hoot, something that was partly masked last year because Kidd and Carter were two of the three best rebounding guards in basketball, according to my Rebound Rate statistic. First-round draft pick Josh Boone could help, but we won’t know for a while since he’s out with a shoulder injury.

The two things New Jersey won’t have to worry about are Frank and Jefferson. The 26-year-old Jefferson should be entering the apex of his career in the next year or two, and his steady improvement in his time as a Net has him on the cusp of an All-Star berth. Meanwhile, Frank has established himself as one of the game’s best young coaches with his defense-oriented, no-nonsense approach. He’s essentially a New Jersey version of Jeff Van Gundy, a tireless worker who never played the game but nonetheless has an incredible understanding of it.

One big advantage for the Nets is their fortuitous placement in the Atlantic Division. With the Knicks, Raptors, and Sixers in various stages of bailing water, the only real threat for the division crown is a young, improving Celtics team. Thus, the Nets could wind up with a top-four playoff seed even if their regular season ends up being a disappointment.

But at this point, I see disappointment as a fairly likely scenario. Even if Carter and Jefferson play to their full potential and Kidd holds off Father Time for another year, it’s tough to imagine the Nets maintaining their cherished contender status. The frontcourt is a huge weakness, and the fortunate run of good health from the Big Four a year ago largely masked how incapable the bench is of stepping up in their absence. Unless the kids are a whole lot better than advertised, a slip back toward .500 seems inevitable.