The idea of Reggie Miller contemplating a comeback could be seen as a joke. Instead, it’s the start of a trend. Charles Oakley, 43, Allan Houston, 36, and Shawn Kemp, 37, are pursuing comebacks. And Penny Hardaway, 36, has signed a nonguaranteed contract with the Miami Heat.

This is going to give the expression “past his prime” a whole new dimension. Is age really nothing but a number?

There are all kinds of temptation to see the best in these attempts. Houston and Hardaway had their careers cut short by injuries. Oakley and Kemp never won a ring, though both reached the finals.

Also, age isn’t what it used to be. Phoenix Suns guard Steve Nash turned 30 in February, often the age at which the skills of many point guards go into freefall. But Nash resisted that gravity, elevating his game three seasons in a row, and winning the Most Valuable Player award in two of them. Meanwhile, baseball is chock-full of pitchers in their late 30s and early 40s. Advances in medicine and science make it seem as if some sort of extended youth is truly possible.

On the downside, there are simply four words to offer: Michael Jordan, Washington Wizards. Jordan came out of retirement to join the Wizards’ roster when he was 38 and played two seasons. In both he was productive and even deserving of an all-star selection. However, “productive” is a near insult when compared with his prime, when he was one of the most dominant players to ever grace any team sport.

The player efficiency rating is a metric developed by my colleague John Hollinger to measure a player’s production on a per-minute basis. The league average is 15. At his peak, Jordan posted a PER of 31.7. During his days with the Wizards, his PER topped out at 20.8 during his first season back. That’s a fall off of over one-third. What would each of these comeback candidates be if they suffered a similar decline?

As every Knicks fan should be quick to note, Oakley’s contributions between 1988 and 1998 went well beyond the stat sheet. He was the hustling heart, soul, and muscle of the team. He had great skill, too, which is amply measured by his stats. Oak’s peak PER came in his rookie season, when he posted a 16.5. Were he to return as gracefully as his former teammate Jordan did, he would post a PER of 11, well below the league average. What’s worse is that Oakley, in his final seasons, performed far worse than that, posting PERs of 8.1, 8.3, and 6.6 in brief stints in Houston, Washington, and Chicago, respectively. It’s hard to see what can result from this comeback attempt, beyond an increased visibility that might result in an on-air job.

Someone has to say it: Allan Houston isn’t on the comeback trail for the money. The recipient of the most outrageous contract ever lavished on a player for a local basketball team, Houston is financially secure and even has a job with ESPN. Devastating knee injuries cut his career short and he retired after missing 94 games in his final two seasons. Houston’s best PER came late in his career, 17.7 in the 2002–03 season, which may lead him to think that it was only the injuries that obstructed a fine late-career run. Assuming he’s healthy, though, his PER likely wouldn’t exceed 11.8, which would almost certainly mean a shooting percentage below the league average. If Houston isn’t a sharpshooter, then he’s worthless to any team at this stage in his career.

Kemp wasn’t done in by injuries. Instead, it was his own lack of self-discipline that ended his career. Beset by weight problems and drug busts, the player — who at his peak was something of a precursor to Amare Stoudemire — became the butt end of jokes (no pun intended). He launched a comeback attempt last season only to have it derailed by an arrest on drug possession in Houston. Kemp’s best season came in the lockout-shortened 1999 campaign, when he posted a 23.6 for Cleveland. He was managing barely half that when he last played in the NBA, but presuming the weight and drug troubles are over, there’s actually reason to think that Kemp might be a serviceable reserve for the right team.

Hardaway has already signed up to be a reserve with the Heat, a move that — given the horrific condition of his knees — makes little to no sense. At his peak, with a 24.6 PER in Orlando in 1996, the guard was a superb player. But he posted PERs of less than half that for each of his last three seasons and hasn’t been above the league average since turning 30 five years ago. The Heat bench is thinner than Calista Flockhart, but that’s no excuse for signing a player who was last good when “Ally McBeal” was a hit.

There are several retired players who might provide a good fit on a return engagement with the league, most notably forward Keith Van Horn and guard Tim Hardaway. Word on the grapevine, though, is that Van Horn grew weary of the travel. Hardaway probably torpedoed any comeback chances with his homophobic remarks following the publication of John Amechi’s “Man in the Middle.”

These comeback attempts are hopefully more than publicity stunts, but my method was the gentlest I could find. If you used each player’s career PER or their last season, then these comebacks look entirely like vanity projects. If any of this goes well, though, then maybe ‘Lil Penny, Penny Hardaway’s wisecracking puppet sidekick from his mid 1990s Nike ads, will also make a comeback. After all, age is less of a barrier in advertising.

mjohnson@nysun.com