Too bad the schedule makers aren’t psychics, huh? The networks scheduled a Heat-Cavs Christmas Day game expecting a showdown between the past two Eastern Conference champions. Instead, it got a snoozer befitting of two teams with combined records of 21–37, as both teams are in danger of missing the playoffs.

Our Martin Johnson eloquently outlined the Heat’s woes a week ago, but the Cavs’ decline has been even more perplexing. At least in Miami’s case the handwriting had been on the wall all summer, as the Heat were swept in four games in the first round of the playoffs by Chicago (um, speaking of disappointments…) and did little but get older in the offseason.

Cleveland, however, was coming off the franchise’s first-ever trip to the NBA Finals. With arguably the game’s single-most talented player in 22-year-old phenom Le-Bron James and an underrated frontcourt, the worst-case scenario in the minds of most was that this team would make a third straight trip to the conference semifinals.

That could still end up being the case by year-end, but the Cavs are a long, long way from contending for anything important at the moment. It isn’t just that the Cavs were 13–16 heading into last night’s tussle in Dallas — a record that, miraculously, still has them in the no. 8 slot in the East. It’s how they ended up there that has been so disappointing.

For starters, they’ve completely lost their identity as a defensive team. Last season, the Cavs ranked fourth out of the league’s 30 teams in Defensive Efficiency, my measure of a team’s points allowed per 100 opponent possessions. That enabled them to reach the Finals despite an offensive attack that consisted mostly of everybody standing around watching James.

This year, the slippage has been unbelievable — all the way down to 26th. On many nights they simply aren’t competing at that end, with last week’s embarrassing noshow against the Knicks being a prime example.

Offensively, little has changed. The Cavs rank 20th in Offensive Efficiency, which isn’t good. But they weren’t good a year ago, either. Once you factor in the five games James missed with a finger injury, you have to think they’ll finish the season in the middle of the NBA pack again.

But the offensive shortcomings seem more glaring because the D can’t offset it, and because so few players are contributing. James has been playing out of his mind and would be an MVP shoo-in if his team would win a game once in a while. But Cleveland has only three other players averaging double figures, and only one other besides those who contributes in other categories (reserve big man Anderson Varejao). The rest do nothing at all.

I’m not exaggerating: Every other player on the roster has been horrid, especially in the backcourt. Larry Hughes — he of the five-year, $60 million contract — is shooting 32.5% and openly complaining about his role. Sounds like he’ll be a Knick any day now. Sasha Pavlovic is at 33.8% and has been noticeably less proficient on D, but somehow he has kept a spot in the starting lineup all the while.

Perhaps that’s because it’s been a bad year to be a Brown in Cleveland, at least if you don’t play football. Potential replacements Devin Brown (37.6%) and Shannon Brown (38.5%, no relation) have provided little incentive for Coach Mike Brown to change the lineup, especially with the latter seemingly in a contest with Hughes to see which player can take the most ill-advised shot.

Glass-half-full types will point out that the Cavs went 0–5 when James was out with a finger injury, and are 13–11 when he plays. There are two problems with this analysis. First of all, 13–11 still isn’t good, not when you’re a defending conference champion. Second, you can’t just assume your best players will play all 82 games. Every team has injuries to key players, and the good ones scrape out a few wins while their stars on the shelf.

Fortunately, some help is on the way. Varejao signed two weeks ago after a protracted holdout; his energy and proclivity for drawing offensive fouls should give the defense a boost. And sharpshooting power forward Donyell Marshall is due back from a wrist injury soon, which will add a much-needed scoring threat to the proceedings.

Yet the effort level on D has been so bad that one wonders if Brown is in danger of losing his team. Much like the recently deposed Scott Skiles did in Chicago, he’s stayed the course with what worked last year for too long instead of shaking things up — with Pavlovic’s continued presence in the lineup the most obvious example.

And when Brown has shuffled the deck, he’s taken the time-machine approach of going with what worked last year instead of what’s working now. He recently moved Daniel Gibson to the bench to start Hughes; this recreated last year’s starting five but replaced a modestly effective player with a disastrously bad one.

Meanwhile, vets Damon Jones, Eric Snow, and Ira Newble have mostly stayed nailed to the pine. On most teams this would go without saying, but on this one they’ve been the least awful of the bunch thus far — so if you believe in merit-based playing time they deserve to play.

As far as quick fixes, few seem on the horizon. While the Cavs have offered Hughes to anyone with a Blackberry and are hoping to procure guard help, their cap situation means that most of the change has to come from within.

That, in turn, means the laser beam is pointed straight at Brown. Last season, he was criticized for an unimaginative offensive approach, but even his harshest critics conceded that his defense was rock solid. Much as with Skiles, however, it appears that rock has crumbled before our eyes. As with Chicago, there were contract issues and other distractions that contributed. But ultimately, it’s the coach’s job to keep the players focused on the game and not the noise surrounding it.

Last year Brown did that as well as anyone — no easy feat with the media circus that follows King James. But this year has been a polar opposite. Last year’s success means Brown has a longer rope than Skiles did, but if the Cavs don’t begin defending with the passion they showed a year ago he’ll meet a similar fate.

jhollinger@nysun.com