There are certain things you expect during the NBA playoffs. You expect close, hard-fought games. You expect the intensity level to go through the roof. And you expect dramatic finishes and compelling stories.

We’ve had all that, but we’ve also had something you absolutely don’t expect — teams crushing their opponents on the glass like a varsity team playing the JV. In three of the four second-round series in these playoffs, the story has one been one of complete domination of the backboards by a team that’s taken a 2–0 series lead.

While Utah’s backboard dominance of Golden State was expected, and perhaps Detroit’s board ownership of Chicago isn’t altogether shocking either, the local club doesn’t have such an excuse. As the Nets head into tomorrow’s Game 3 at Continental Airlines Arena (5 p.m., ESPN), they’re still having nightmares about floppyhaired forward Anderson Varejao’s beating them to one rebound after another during the second half of Game 2.

As TNT analyst Doug Collins repeatedly stated in Tuesday night’s 102–92 loss in Cleveland, New Jersey’s undoing was its inability to put a body on Varejao when the shot went up, allowing the 6-foot-11-inch Brazilian to come flying in and snatch away offensive rebounds.

As a result, Varejao grabbed six offensive boards in just 17 minutes — and in the process, doubled the output for New Jersey the entire game. Overall, the Cavs grabbed 19 offensive rebounds on their 48 available misses, a totally unacceptable 39.6% offensive rebound rate (the league average this year was 27.1%).

Worse yet, New Jersey’s inability to rebound its own missed shots stood in stark contrast to Cleveland’s success. The Nets grabbed three offensive boards all game, on 33 misses, for a pathetic 9.1% offensive rebound rate. Cleveland’s enormous rebound advantage allowed the Cavs to steal a game in which they were otherwise outplayed.

Just think — when was the last time you saw a team outshoot its opponent from the field, the 3-point line, and three free-throw line and still lose by double figures? New Jersey pulled off that mean feat, wasting some precision offense in the process.

The Nets shot 52.3% from the floor to Cleveland’s 44.7%. They made 8-of-14 on 3-pointers, had 22 assists to the Cavs’ 19, and missed four fewer free throws. But sometimes quantity is better than quality, and this was one of those cases. The Cavs took 20 more shots than the Nets because of the rebound gap, providing the victory margin.

Game 1 of the series was just as bad. The Cavs’ 81–77 win came about largely because they snagged 20 offensive boards — this time Zydrunas Ilgauskas (8) and Drew Gooden (6) did most of the damage. Between the two games, Cleveland has rebounded 40.6% of its misses and attempted 29 more shots than New Jersey.

First, a tip of the hat is in order for Cleveland. Ilgauskas and Gooden are two of the game’s best offensive rebounders, with each ranking in the league’s top 15 in Offensive Rebound Rate during the regular season (my measure of the percent of available rebounds grabbed by a certain player), and Varejao wasn’t far behind. Certainly this is a formidable foe on the glass.

In addition, one prerequisite for an offensive rebound is a missed shot, and the Cavs certainly have been missing their share — an amazing 52 Cleveland shots failed to find the mark in Game 1, for instance.

But defensive rebounding wasn’t supposed to be a problem for the Nets no matter the opponent. New Jersey’s 74.4% Defensive Rebound Rate was bettered by only five other teams this season. That trend continued in the first round, where the Nets grabbed 81.0% of Toronto’s misses — the best rate of any team in the first round of the playoffs.

Thus, this is a far more hurtful situation than it is for, say, Golden State, who went into its series with Utah expecting to be pounded on the boards. In this case, Cleveland is turning the series upside down by taking one of the Nets’ biggest strengths and turning it into a profound weakness.

The key, as Collins pointed out, is that the big guys aren’t getting the job done. New Jersey’s frontcourt rebounding totals were especially pathetic — Mikki Moore, Jason Collins, and Josh Boone combined for only four defensive boards in each of the first two games, a disgraceful performance by any standard.

It’s true that the Nets are an unusual rebounding team because they depend so heavily on their guards to rebound — Jason Kidd led the team in this category from the point guard spot, believe it or not, and only Kidd and the long-injured Nenad Krstic topped Vince Carter. But for that to work, the big guys have to wall off Cleveland’s guys — that way the guards can fly in for the carom if the bigs can’t get to it.

At the moment, they aren’t doing it, and the results have been embarrassing. Hyperactive players like Varejao and Gooden, who often were outside the key when a shot went up, have repeatedly raced in past flat-footed Nets to snare the board.

In fact, if you just look at the frontcourt trios on each side, the rebound margins are especially staggering. Cleveland’s three have combined for 27 offensive boards in the two games; the Nets, a measly eight defensive rebounds. Yes, Virginia, they’re getting outrebounded more than 3-to-1 in their own end.

Perhaps the worse news is that I’m not sure of a good prescription. It’s not like the Nets can go to alternate personnel — the next frontcourt sub, Clifford Robinson, is an even worse rebounder than the guys he’d replace.

No, the solution to this conundrum has to come from within. Somehow, the Nets’ frontcourt players have to match the Cavs’ relentless energy under the boards and combine that with the execution of fundamental blockouts to render Cleveland’s edge in athleticism useless.

The good news here is that if they do those things, New Jersey still can win this series. Both games this week were there for the taking, and the Nets should have the upper hand in the backcourt all series long.

But in a must-win Game 3, the first must is keeping the Cavs off the glass. If the Nets do it we’ll have a great series to watch. And if not? Golf season starts on Tuesday.

jhollinger@nysun.com