Every pro wrestler has a shelf life.

Despite how big, how famous or how valuable a guy is, eventually the sun will set, and the time will come to move on.

It happens to the best, and for those men and women who have given their all to the business they love, the understanding exists that sooner or later, it will be time to hang up the boots and move on with the next chapter of their lives.

It’s not an easy day to confront, nor is it an easy day to accept.  But, to fight it is to prolong it, and to prolong it means making the eventual departure that much harder later on.

One day, the last match will happen, and the final bell will ring.  It is an inevitable part of the business.

And, one day, the final bell will sound for John Cena.

Take a moment and think about that.  Imagine the day that John  Cena, perhaps a little older, a little grayer, and a little slower in the step, getting his arm raised in victory one last time.

Imagine the locker room clearing out the next night on WWE Raw, as one by one the Superstars climb into the ring, and thank John for all the he’s done, wishing him good luck in the future.

Imagine WWE without John Cena.

It’s almost impossible to even comprehend at this point, especially considering that John has been in the company since 2002, and been considered the top guy since his first WWE Championship win in 2005.

Ten years of denim shorts, baggy shirts, and never-say-die attitude.  And, in all that time, WWE fans who both love and hate John, have been so obsessed with him as a performer, and his top spot, that few ever seem to talk about the day that it all comes to an end.

Perhaps because it seems as though he will never leave?

John Cena is a lifer, a man who is 100 percent dedicated to the business, and to the house that McMahon built.  He eats, breathes, lives WWE, and is as much a part of that company as it is a part of him.

Let’s face it.  At this point, Cena should be the WWE logo, like Jerry West in the NBA.

The truth is, when John’s time does come to walk away from the ring, will he really walk away from WWE?

As difficult as it is for fans to see a time when he’s not an active competitor, it’s even tougher to imagine Cena not being involved with WWE in some fashion.

Whether it’s as a road agent, an executive behind the scenes, or as an on-air personality, John likely has a guaranteed position, just waiting for him, in the largest pro wrestling company in the world.

But, what if he left today?

What if John Cena, the much debated, controversial, yet bankable, face of WWE, had a career ending injury, much like Edge did, and was told by doctors “that’s it, you’re done?”

What would WWE do next?  Who’s ready to slide in and take the crown laid down by John, and continue leading the company into the future?

Does WWE even have anyone who fits the bill?

CM Punk, arguably the second main Superstar in WWE, seems to hinge on the perceptions of a rabid fan base who one minute love his unpredictability, and applaud his rise to the top, then criticize him for somehow becoming stale when he gets there.

Randy Orton, who at times, has been neck and neck with John in recent years in terms of fan approval, and overall contributions to the company, simply cannot stay out of trouble long enough to warrant consideration for top billing in WWE.

Sheamus, the current World Champion, is a fan favorite, and there is no doubting how far he’s come, and the level to which he has now ascended, through hard work and determination.

But, the fact is, he has just now come into his own in WWE, and perhaps does not have enough to carry the weight of the company on his shoulders.

Add to this an eclectic mix of Superstars, including Alberto Del Rio, Daniel Bryan, Zack Ryder, Cody Rhodes, Dolph Ziggler, and a few others, and the question of “who’s ready now,” becomes a bit hazy, to say the least.

Is the man who will one day replace John Cena even currently employed by WWE?

WWE is rolling along right now, doing what they do, week in and week out.  Sometimes the ratings are good, sometimes they’re not so good.  But, for a good bit of the time, Vince McMahon runs his company on one simple philosophy: throw it to Cena, and we’re in business.

There seems to be no plan B.

We’re all just getting older.  The stars I grew up watching, including Ric Flair, Dusty Rhodes, the Road Warriors, Barry Windham, Wahoo McDaniel, Nikita Koloff, Magnum TA, and the Midnight Express, are all names of the past.  Some have moved on.  Some are still around.  But, it’s not the same as it used to be.

Reading this piece right now, there is a younger fan, perhaps the same age I once was when I fell in love with the business.  For that fan, CM Punk, Sheamus, Randy Orton, Cody Rhodes, and John Cena are the biggest names he knows.  Some will move on.  Some will stick around.

But, one day, for those fans, it will not be the same as it is now.

John Cena, for better or worse, is the most visible, most important WWE Superstar that some fans know.  He is Mr. WWE, and the world of professional wrestling revolves around him.

But, one day, John will work his last match.  One day, he will kiss the dog tags for the last time, and his legacy will ultimately be decided by the fans who either paid to see him perform, or to hate him relentlessly.

Until then, the sun still shines on John Cena.  At least for now.