Will Marlins be sideshow or headliner?

Everyone knows the Miami Marlins will be entertaining. As the subjects of a reality show — Showtime’s “The Franchise” — the Marlins probably will make the Kardashians look well-adjusted.

The bigger question is, will the Marlins be any good?

The answer hinges not on the team’s most colorful characters — Ozzie and Hanley, LoMo and Big Z — but on the low-key, oft-injured right-hander, Josh Johnson.

If Johnson makes 30 starts, a plateau he has reached only once in his career, the Marlins should contend.

If not, we’re looking at a potential 25-man pileup inside the Marlins’ new ballpark in downtown Miami.

Never mind shortstop Jose Reyes, nicknamed “Mr. Energy” by left fielder and social-media deity Logan Morrison.

Never mind right fielder Mike Stanton, whose powerful abdominals look not like a six-pack, according to owner Jeffrey Loria, but a “distributorship.”

And never mind closer Heath Bell, who says he is not in his prime or past his prime, but in his “midlife-crisis prime.”

The most important Marlin is Johnson, who did not pitch after May 16 last season because of inflammation in his right shoulder.

Johnson, 28, threw live batting without incident Tuesday, prompting Loria to pronounce that he will be “fine.” Well, that’s easy to say now. Check back in June.

“Josh Johnson, if he gets hurt and misses significant time, it’s going to be tough to do what we want to do,” left-hander Mark Buehrle says.

Every team with an ace is in the same position, but Johnson is more fragile than say, CC Sabathia. Only once has Johnson remained healthy for an entire season, in 2009.

The Marlins’ predicament, then, is twofold.

They’re not the Philadelphia Phillies, who boast multiple aces. And they’re not the Tampa Bay Rays, who go seven or eight starters deep.

The rest of the Marlins’ rotation — Buehrle and righties Anibal Sanchez, Ricky Nolasco and Carlos Zambrano — should be quite presentable. But what are the odds that all five starters will be healthy and effective all season?

Therein lies the problem.

The dropoff to the Marlins’ other rotation candidates — left-handers Wade LeBlanc and Sean West and righty Alex Sanabia — is considerable. Yet, the team likely will need one of them before the season is over, and maybe all three.

So, it’s easy to see how quickly the Marlins can teeter. But it’s also easy to see why they are so excited about their potential. The offense, in particular, could be downright electric.

Reyes already is making an impact, practicing at game speed, energizing his teammates. Guillen notes that the shortstop is pushing the temperamental Ramirez to have fun. Morrison adds, “He came in the locker room that first day and everyone brightened up.”

“I’m happy all the time, but I can’t smile that much,” Bell says.

Of course, the Marlins committed $106 million to Reyes not for the difference he will make off the field, but the tone he will set at the top of the order.

Guillen, who grew frustrated with his lumbering White Sox teams in Chicago, says he wants even Stanton and Morrison running. Emilio Bonifacio or Omar Infante will hit second behind Reyes, but Guillen says he is leaning toward Bonifacio for the speediest 1-2 punch.

From there, the lineup is rather imposing.

Ramirez, who is coming off surgery on his left shoulder but looks terrific in early drills, will hit third, followed by Stanton, Morrison, Gaby Sanchez, John Buck and Infante (or Infante and Buck).

One concern: The Marlins lack a quality backup at short if Reyes gets injured. Guillen says he will not move Ramirez back to short from third base. But if Bonifacio is in center, Donnie Murphy would be the leading alternative to Reyes.

The emergence of another center fielder could alter the equation, and Bell believes that Aaron Rowand, a non-roster invitee, could become Comeback Player of the Year. Chris Coghlan, coming off two knee surgeries, is another possibility. But Bonifacio, coming off a breakout season, deserves to play every day.

The bullpen, which ranked sixth in the NL in ERA last season, is another potential strength. Bell will close, and the Marlins are deep from both the right side (Edward Mujica, Ryan Webb, Steve Cishek) and left (Mike Dunn, Randy Choate). In addition, many of their best prospects are hard-throwing relievers.

The wild card is Juan Carlos Oviedo, the pitcher previously known as Leo Nunez, who is trying to obtain a visa to return to the US. Guillen jokes that he would use Oviedo in the seventh and Nunez in the eighth, saying he would have “two guys in one . . . 13 pitchers, 12 bodies.”

Kidding aside, the Marlins’ party line is that none of their players needs to have a career year; if everyone merely performs to expectations, the team will contend.

Sounds reasonable enough, but one player looms above all.

Not Hanley, LoMo, Big Z or any of the Marlins’ other reality-TV stars.