For half a season, the Miami Heat have hung on by a fingernail.

They’ve stapled together a stop-gap rotation, eked out a few close wins, and kept themselves reasonably close to the playoff race at 19–22, just a whisker behind New Jersey and Toronto for the East’s final playoff spot. All of it was done with the thought that once Shaquille O’Neal came back, the Heat would resume their rightful place at the top of the NBA universe and start their quest for a second straight championship.

But their logic may have been flawed. The first step in Shaq’s return showed why, as he was anything but dominant in a 96–94 overtime loss to the Pacers on Wednesday. While O’Neal looked noticeably less heavy than he seemed at the beginning of the season, he wasn’t exactly light on his feet.

His final tally of five points, five rebounds, and two turnovers in 14 minutes in his return underwhelmed, particularly since the Heat began ceding a 20-point second-half lead during his stretch of playing time in the third quarter.

But while O’Neal’s play itself disappointed, the game was intriguing, because it showcased both how much resilience the Heat have displayed this season, and how further they still have to go to resemble anything close to last year’s squad.

On the one hand, the yeoman work they did to pull things together after a dreadful start has to be applauded. Dwyane Wade put the team on his back and led them back into the playoff race, even more than he did in the Finals last June.

Miami also made some tweaks to help it stay afloat. Antoine Walker got off to a disastrous start, bricking one 3-pointer after another and was suspended for failing to meet the team’s conditioning goals. But the result was an opening for sharpshooter Jason Kapono (who is hitting a ridiculous 55.5% on 3-pointers), and the team seems better off for it.

And when coach Pat Riley checked out to get hip replacement surgery — which some felt he only did because his preferred option, team replacement surgery, wasn’t available — interim coach Ron Rothstein battened down the hatches. He guided the Heat to a four-game win streak on a Western road trip that rekindled their playoff hopes, and perhaps set the stage for Riley to make a soonerthan-expected return.

All that continued on Wednesday. There was Kapono, dropping in 18 points while missing only three shots. There was Alonzo Mourning, protecting the middle in Shaq’s place with five blocks. And of course, there was Wade with 32 points, eight assists, five steals, and three blocks.

But once again, the supporting cast proved to be a long, long way from prime time. My Player Efficiency Rating (PER, a per-minute rating of a team’s statistical effectiveness) showed only three of the Heat’s regulars above the league average of 15.00 — Wade, Alonzo Mourning, and Jason Williams. Several are well below, including two mainstays of last year’s title run, Walker and Gary Payton.

Payton, with a PER of 7.7, is among the worst-performing regulars in basketball. Of late, he’s become petrified to even shoot. A glaring example came at the end of Wednesday night’s game, when Kapono was double-teamed and found a wideopen Payton behind the 3-point line. Five years ago this was a gamewinning dagger; on Wednesday, Payton didn’t even look at the basket and instead threw it right back to Kapono, who missed a contested look at the buzzer.

Additionally, Miami’s finger-inthe-dike job without Shaq may be causing some to underestimate how much work remains to be done. Through 41 games, the Heat had an average scoring margin of -3.6 points a game. Normally this doesn’t produce a record of 19–22, but rather a mark of 14–27, and the fact the Heat didn’t was a fluke.

You may ask how we know this is a fluke rather that the Heat’s “knowing how to win” or their possessing a magical elixir of clutch ability. The reason is that there is no proof — I repeat, none — that outperforming the expected winloss record based on scoring margin is a repeatable skill. Even teams that keep the same personnel for years and develop reputations as great clutch performers — such as the Bulls of the 90s — have failed to consistently outperform (or underperform) in this category. And so we must conclude that the main determinant is chance.

This is important because it alters the psychology of Shaq’s return quite a bit. Since the Heat were at 19–22 entering Thursday, we tend to think of them as roughly a .500 team. And as such, we presume that the return of O’Neal from injury can lift them well above the morass in the Eastern Conference, especially if he comes back as the dominant big man he’s been his whole career.

But if one accepts that the fivegame difference between 19–22 and 14–27 is the result of chance rather than skill, then we have a much different evaluation of Shaq’s impact. No longer is he riding in to lift a .500 team to glory; rather he’s coming to try lift a lottery team closer to mediocrity. Those 19 wins still will help the Heat in their playoff chase, but even if Shaq comes back as his old self it’s more likely they’ll go 23–18 or so in the second half, not on some 31–10 tear. That will put Miami around .500 at year-end, and precariously close to the lottery.

Even that may be a best-case scenario. The fact is, Shaq looks a long way from his old self, and that was true prior to the injury as well. In the four games before he went out, O’Neal shot 45.2%, only took 18 free throws in four games, and had 14 turnovers against five assists. He blamed his performance Wednesday on rust, and that may be true, but one could easily argue that it was just more of the same.

So if you’re looking for the Heat to flip the switch over the final 40 games, you might want to temper your expectations. Despite Wade’s brilliance, this is one switch that won’t be tripped unless the superstar Shaq of old shows up. And on Wednesday at least, he wasn’t Shaq — he was just some random guy named Shaquille.

jhollinger@nysun.com