5 UFC fighters who might retire in 2018

The shelf-life of an athlete or sportsperson competing at the highest level is pretty short. Assuming they start in their late teens or early twenties, most of them perform to the best of their abilities for about 12-15 years. And only IF they don't suffer any critical injuries along the way. That is a very small window in which they must make enough money to sustain them for life and of course, leave their mark on the sport.

In this light, it is obvious that MMA fighters are an aberration. Not only have we seen fighters compete at a high level well into their forties, but it's in a sport where the training and the end game entail the breaking of the mind and the body. If that's not a testament to their toughness, what is?

But no matter how skilled they are, how intelligently they preserve themselves or how long they've stayed unbeaten, fighters are after all human. There is one unvanquishable challenger against whom the harder you struggle, the harder you fall and that is time. So here are 5 UFC fighters who might hang up their gloves in 2018:

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#5 Diego Sanchez

The Ultimate Fighter 1 is historic because of its finale, where Forrest Griffin and Stephan Bonnar put on a barnburner that basically brought the UFC back from the dead. Griffin won the fight and earned a 6-figure contract with the UFC, but Dana White and the Fertitta brothers were so impressed with Bonnar's heart that he was awarded a contract as well.

What a lot of people don't remember is that Diego Sanchez was the winner of the Middleweights who competed on the show. In fact, he's the only contestant from the show who's still active in the UFC, thirteen years later. Wondering what keeps Sanchez going? Probably the same red-hot passion that carried him to a rear naked choke win in his MMA debut (for which he earned $600) despite a broken heel.

Throughout his career, Diego Sanchez has fought in four weight classes and has won an astonishing seven Fight of the Night bonuses, the most in UFC history. Three of those fights, against Karo Parisyan, Clay Guida and Gilbert Melendez, went on to win Fight of the year and will find their place among the greatest battles of all time.

Now 36, Sanchez has lost 3 of his last 4 fights with two of them ending with him being brutally knocked out. The amount of damage he's absorbed because of his take-two-to-give-one style of fighting would've definitely taken a heavy toll. Despite this, he certainly won't be cut from the UFC but could consider calling it a day soon to save himself unnecessary harm.

A title has eluded him, but he's spent 13 of his 15 years as a professional fighter in the UFC, a boast not many others can make.

#4 BJ Penn

In its infancy, mixed martial arts was perceived stereotypically as a battle for dominance between two human gorillas. And it actually was, until the likes of BJ Penn came along. Dana White attributes the ascent of the lower weight divisions to Penn and many regard him as the greatest Lightweight of all time (Khabib says "This is number one bulls***").

With a black belt in Brazilian Jiu Jitsu after just 5 years of training and becoming the first non-Brazilian in history to win the World Jiu Jitsu championships, Penn showed that his nickname "The Prodigy", was an understatement.

Penn burst on to the MMA scene when he moved up a weight class and upset the seemingly invincible 5-time Welterweight champ Matt Hughes. He then made history by winning the Lightweight championship and becoming the 2nd man in UFC history to hold belts in different weight classes. Penn holds wins over the who's who of the UFC, beating the likes of Kenny Florian, Diego Sanchez, Jens Pulver, Joe Stevenson and Sean Sherk, to name a few.

He has hinted about retiring more than once, but you don't need to read his autobiography, "Why I Fight: The belt is just an accessory", to know why he soldiers on - the man himself has emphasized his belief that he is a born fighter and continues to do it because he loves it.

Penn was inducted into the UFC Hall of Fame in 2015 by former foe Matt Hughes. The last few years haven't been kind to the once mighty Hawaiian - he's lost his last five fights and at 39, could soon be walking off into the sunset.

#3 Anderson Silva

Anderson Silva's story is among the most inspiring in MMA - he grew up in a Brazilian slum unable to afford martial arts lessons and went on to become who many consider the greatest mixed martial artist of all time.

Silva's impoverished childhood aside, he also hit a lot of bumps early in his MMA career. He was cut from PRIDE and almost quit the sport, but was encouraged by legend Minotauro Nogueira to keep fighting.

His perseverance paid off and Silva made history with the then longest title reign in UFC history at a mind-numbing 2457 days! The things he's done in the octagon are one-of-a-kind and for many, impossible to duplicate. What makes his legacy all the more impressive is the fact that he debuted in the UFC and ruled the Middleweight division in his mid-thirties, the twilight of most sportspersons' careers.

But Silva's fortunes have taken an unimaginably dire turn in the last few years. "The Spider" has lost 4 of his last 6 fights and now, aged 42, is looking at a possible 4-year suspension for PEDs. It seems Silva himself is implying retirement because he's ready to trade in the 4-oz gloves for 10-ouncers to achieve his longtime dream of facing another legend, Roy Jones Jr.

#2 Michael Bisping

For the longest time, Michael Bisping was a fighter the fans loved to hate. But all that changed when at UFC 199, at age 37, on a few weeks' notice, "The Count" knocked out the monstrous Luke Rockhold in one of the greatest upsets in MMA history and became the first British champion in UFC history. Not to mention, he brought some much-needed energy to the 185-lbs ranks.

Bisping won season 3 of "The Ultimate Fighter" as a 205-pounder but dropped down to Middleweight, which back then was one of the most cut-throat divisions in the UFC, with the likes of Wanderlei Silva, Dan Henderson, Chael Sonnen and Vitor Belfort in it. For a long time, he was considered somewhat of a gatekeeper, but in the past couple of years, has become a potential UFC Hall of Famer.

The sharp-tongued Brit has proved to fans and the UFC his loyalty and commitment to the sport. Nowhere was this more evident than when he faced the young, hungry and dangerous Kelvin Gastelum just 2 weeks after losing his belt to GSP, in order to salvage the main event of UFC's first event in Shanghai.

Bisping has declared that he wants to have one last fight, on home soil and seeing as he's not part of UFC's upcoming event in London, it could mean that he's given in to the pleas of his loved ones and decided that his fighting days are over.

#1 Vitor Belfort

While all the other fighters on this list have been calculated guesses, Vitor Belfort's last fight has already been announced.

Belfort donned the MMA gloves at just 19, an age when most others would've been wondering which colleges to apply to. He proved himself to be every bit "The Phenom" his nickname said he is, by becoming the youngest fighter to win a UFC tournament.

The scalps the Brazilian has collected in both PRIDE and the UFC could fill a wing in a Hall of Fame - Randy Couture, Wanderlei Silva, Dan Henderson, Rich Franklin, Rumble Johnson, Luke Rockhold and Michael Bisping are some of them.

After oscillating on the topic of retirement, Belfort will step into the octagon for the final time against fellow Brazilian legend Lyoto Machida at UFC 224 in his hometown of Rio De Janeiro.