As far as midterm report cards go, this one is a doozy.

The Nets reached the halfway point of the season at 18–23, and that only tells part of the story. The real downer is not that they’re 18–23 in their past 41 games, but that they have almost no chance of matching that in their next 41 games. New Jersey’s six-game losing streak heading into Thursday’s contest at Golden State only confirmed what a lot of people have suspected for a while — this is a bad team, folks, and it’s not going to get better.

Of late, it seems they’ve surrendered to that premise a bit too readily. In a four-game stretch, the Nets surrendered 111, 120, 116, and 128 points; three of the defeats came against losing teams. And that’s what is most troubling about New Jersey’s play of late — not that they’ve been much worse than expected, but that they don’t even look like the Nets.

You remember the Nets, right? Under Lawrence Frank, they’ve been a team that hasn’t always been easy on the eyes, especially in the half-court offense. But they always defended. They’ve been in the top half of the league in Defensive Efficiency (my measure of a team’s points allowed per 100 possessions) every year he’s been in the Swamp, and for most of that time they’ve been way up near the top.

Even last year when they slipped to “just” 14th, there were obvious reasons for the decline — the ankle injury suffered by Richard Jefferson that limited his ability to stick with top-flight scorers, and the loss of power forward Nenad Krstic to a knee injury.

But this year, they’re 25th. Watching the Nets’ pathetic effort in the Sacramento game had to come as something of a shock to long-time observers. To review the carnage, New Jersey gave up 57.5% shooting, including 15-of-24 on 3-pointers, and allowed 128 points in a 34-point spanking by a team with the 11th-best record in the West.

That 3-point percentage sticks out especially, because it’s been an issue all season. Even before the Kings debacle, the Nets were 24th in 3-point defense at 37.5%. The Nets also have the fourth-highest right of opponent free-throw attempts — .375 for every opponent field-goal attempt.

Believe it or not, these two items are related. A lot of teams both surrender a lot of 3s and a lot of free throws, and those teams have one thing in common — their frontcourt isn’t any good. The open 3s happen because the bigs require double-team help against post players, and the free throws happen because they have to foul out of desperation when they single-cover.

In New Jersey’s case, there are obvious reasons behind this. Krstic is still on the shelf while he tries to mend his knee, although he’s been practicing with the team and may return to action soon. While he’s out, the Nets are going with a starting lineup of Josh Boone and Sean Williams. In time that may be a decent combination; for now, they’re a bit undersized and hugely inexperienced, and that’s a problem.

The bigger problem, however, is that there isn’t a solution available. Remember, coach Lawrence Frank only went to this combination out of desperation because he needed to jump-start the offense. The Nets were second-to-last in the league in Offensive Efficiency when he opted to yank Jason Collins and Malik Allen and replace them with the Boone-Williams combination.

The move had its desired effect in the sense that it improved the offense a bit — New Jersey is 26th in that category now. But it made a defense that was already fairly marginal into something unseen around here since the Marbury days — one of the worst units in the league.

Some have suggested the defensive decline is a result of Lawrence Frank’s message getting stale, or of Jason Kidd’s resignation to the Nets’ mediocrity, but I don’t think that’s it. It’s not like the defensive struggles are a recent phenomenon — for instance, a month ago, the same Kings team came into the Meadowlands without three starters and made 13-of-21 3-pointers and scored 106 points in yet another depressing Nets loss.

It would be awesome if effort was the problem, but isn’t. Unfortunately, Kidd is right: This is who the Nets are. Vince Carter and Kidd remain good players but they’re no longer superstars, so they can’t sustain the Nets’ former level of play without a huge push from the other guys … and the other guys don’t have the goods to do it.

The team’s talent base has declined to the point that Frank basically has two options. He can use players like Collins, Antoine Wright, and Darrell Armstrong, and send out a lineup that is barely passable defensively but among the very worst in the league offensively. Or he can use players like Nachbar, Boone, and Sean and Marcus Williams, and send out a lineup that is barely passable offensively but among the very worst in the league defensively.

In other words, he faces a choice not between losing and winning, but between losing 90–80 or losing 120–110.

While the Nets are on a 36-win pace that gives them some kind of vague hope of making the playoffs, the cruel truth is they might not even get to 30. Look, I’m searching high and low for optimistic trends, and I’m not finding much. They’re 26th in Offensive Efficiency, 25th in Defensive Efficiency, and 26th in scoring margin. They’ve played more home games than anyone except Charlotte or San Antonio and now will have to navigate through much of the second half out of a suitcase. And their average opponent so far has a .489 winning percentage, so it’s not like the schedule is killing them.

In fact, the only reason they’re even 18-23 is because they’re 12–3 in games decided by five points or less — a glorious fluke that has almost no chance of repeating in their next 15 such games. Basically, they aren’t good, and even if Krstic returns they won’t get a whole lot better.

In that sense, maybe this six-game losing streak is a blessing in disguise. For over a year, the Nets team president Rod Thorn has tortured himself over whether to blow up the nucleus and start over. Now, we don’t have to wonder.

He walked the full mile with this group, won two conference titles with them and established a winning culture in a place that had become synonymous with losing — so much so that most national observers have been slow to realize the extent of the rot.

With the recent streak, he needn’t waffle any longer. It’s over, Rod, and there’s no shame in that. Let’s allow Kidd and Carter to finish their careers with contenders and not prolong the agony.

jhollinger@nysun.com