In what has already been declared the biggest fight in mixed martial arts history, former two-division champion Conor McGregor returns to the Octagon on Saturday for the first time since 2016 when he faces current lightweight king Khabib Nurmagomedov. The pairing between likely the two best 155-pound fighters in the world headlines a UFC 229 card in Las Vegas that is expected to break the company's pay-per-view record thanks to a grudge match that severely escalated in April when McGregor attacked a bus carrying Nurmagomedov days before UFC 223 in Brooklyn, New York. 

A felony arrest and a few court dates later, we have ourselves a fight. But just as importantly, we also have a strong co-main event and fairly exciting undercard packed with interesting storylines. 

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Let's take a closer look at the biggest ones entering Saturday at T-Mobile Arena. 

1. Has Conor McGregor bitten off more than he can chew? Two years removed from his last appearance in the Octagon with nothing resembling a tune-up bout to prepare him, the brash Irish star has set himself up for nothing short of a free fall into the deep end against the most dangerous opponent available. Not only is Nurmagomedov unbeaten in 26 fights and quite possibly the most dominant wrestler in the sport's history, his biggest strength just happens to clash with McGregor's most glaring weakness in fighting on his back. 

If that wasn't enough, it's the Russian-born destroyer who enters the fight seeking revenge for McGregor's infamous attack six months earlier. At their September press conference in New York, "The Notorious" spent upwards of 45 minutes poking the bear even more with a stinging -- and very personal -- verbal assault. This is unquestionably the biggest challenge and most dangerous fight of McGregor's career, and a tour de force of his own machismo not to duck it in favor of an easier fight considering the financial leverage he holds following a $100 million windfall in boxing Floyd Mayweather last year. Whether or not McGregor, the betting underdog, can produce magic one more time, he deserves the respect coming back to handle his business in such a risky way. 

2. Make no mistake -- McGregor's return is best for business. Call it cliche or fantasy all you want, but the surprise announcement in August before UFC 227 that McGregor was finally returning set off an audible response of ringing cash registers from company headquarters in Las Vegas that could be heard around the globe. Let's face it, no one has been able to sell pay-per-views in MMA history quite like McGregor, who unofficially accounted for 5.3 million total buys over four UFC fights in an 11-month stretch that ended with UFC 205 in November 2016. His next appearance, in a boxing match against Mayweather last August, produced 4.4 million on its own. 

Just how much did UFC's PPV buys compare since McGregor left two years ago? Of the 23 PPV cards which followed, only three managed to reach 400,000 and just one -- UFC 207: Amanda Nunes vs. Ronda Rousey -- eclipsed one million. It's no secret how badly UFC, which announced a new six-fight deal with McGregor, needs him, which is why it appears anything short of the ownership stake McGregor demanded after UFC 205 isn't off limits. Not only did the company allow McGregor's new line of whiskey a valuable advertising spot on the fighting canvas for Saturday, let's not forget UFC's controversial decision not to punish him in the first place despite a felony attack against his co-workers that caused physical and mental damage.

UFC 229 is Khabib's chance to show everyone who he truly is.  Getty Images

3. Nurmagomedov finally gets his defining fight. It's a notion that may sound a bit ridiculous on the surface since Nurmagomedov is the unbeaten UFC champion at 155 pounds. Yet injury and bad luck have conspired to rob the 30-year-old from one big fight after another, each meant to cement him -- without a shadow of a doubt -- as the most elite lightweight in the UFC. But four years after his breakthrough victory over future champion Rafael dos Anjos, Nurmagomedov still hasn't had that victory. Yes, dominant wins over contenders like Michael Johnson and Edson Barboza reminded us of his toughness and pedigree, but do we really know how good Nurmagomedov actually is? 

Four times he was scheduled to face Tony Ferguson and four times the fight fell apart. Along the way, "The Eagle" missed two full years due to a knee injury and another full year after back surgery. Against McGregor, Nurmagomedov finally gets his chance to show whether he's one of the top pound-for-pound fighters in the world or just a frontrunner against B-level competition. 

4. Tony Ferguson takes big gamble on himself. Riding a 10-fight win streak, there is no fighter more deserving of a title shot in the UFC's deepest division than Ferguson. The problem for "El Cucuy" is there is also no one who has had worse luck trying to secure one. In March 2017, Nurmagomedov withdrew from their interim title fight at UFC 209 after being hospitalized due to a difficult weight cut. After Ferguson returned to claim the interim strap by defeating Kevin Lee seven months later, his fourth attempt at fighting Nurmagomedov -- this time for the full title at UFC 223 -- came to a disappointing halt when he suffered a freak knee injury during a media tour. Not only was Ferguson shamelessly stripped of his interim belt shortly after, but McGregor took his place in line after attacking Nurmagomedov weeks later. 

Yet instead of waiting in line knowing that he's the most deserving to face the winner of Nurmagomedov-McGregor, Ferguson has decided to risk it all by facing former champion Anthony Pettis in the co-main event. At 34 and coming off serious knee surgery, there's no telling whether Ferguson would ever be able to work his way back into a title shot should he lose on Saturday. The matchup also does him no favors considering Pettis has appeared to break free from a recent slump and is starting to look like his former self again. 

5. Derrick Lewis gets a second chance to make a new impression. Let's not pull any punches here, Lewis' decision win over Francis Ngannou at UFC 226 in July was supposed to be a reckless and violent showcase of what makes heavyweight MMA so fun and unpredictable. It was also supposed to declare who might be next in line for a title shot (before former champion Brock Lesnar crashed the party after Daniel Cormier won the championship later that evening). Instead, the fight was anything but reckless, violent or fun. The only unpredictable thing about it was how boring it was as Lewis, who was nursing a back injury, equaled Ngannou's inactivity in a passive and boring sparring session. 

Surprisingly, UFC president Dana White chose to put all the blame on Ngannou in the aftermath while absolving Lewis. The reward for the "Black Beast" is a comeback bout against former Bellator champion Alexander Volkov, who is riding a six-fight win streak. A victory for Lewis, in theory, would likely place him on the doorstep of facing either the winner of Cormier-Lewis or, at worst, former champion Stipe Miocic. Either way, it's a rare second chance for him to let it be known he's next in line while further distancing himself from the Ngannou debacle.