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Stop me if you've heard this one before but former UFC two-division champion Conor McGregor is entering, quite possibly, the defining fight of his career with the future of his elite status at stake.  

It's a narrative we have seen before throughout the unique career of the sport's biggest pay-per-view star. It was a major theme ahead of his double-or-nothing welterweight rematch with Nate Diaz in 2016, his comeback bout following just one appearance in four years entering ahead of his 2020 meeting with Donald "Cowboy" Cerrone and it was even thrown around before his second meeting with Dustin Poirier in January.

McGregor (22-5) will be less than a week out from turning 33 when he faces the perennially game Poirier (27-6, 1 NC) on Saturday in their must-see trilogy fight headlining UFC 264 inside T-Mobile Arena in Las Vegas. And it's the combination of the Irish star's age mixed with his overall inactivity since his career peak in 2016 that has so many questioning whether the days of "Mystic Mac" calling his shots and demonstratively delivering are long, long gone.

Such is the life of such a polarizing athlete whose true value in comparison to the elite competitors atop the sport today can seemingly never be accurately defined.

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According to McGregor's diehard fanatics, the brash Irish star is always one distraction-free training camp away from knocking out anyone he chooses to (provided he has finished walking on water and healing the sick). His detractors, however, believe everything McGregor has accomplished above 145 pounds (where he's just 3-3 since 2016) has been nothing but smoke and mirrors considering he holds just one win at lightweight and hasn't been nearly the same destroyer he was as a featherweight.  

To make matters even more confusing, McGregor's performance against Poirier at UFC 257 just six months ago provided fuel to both sides of the debate. The "Notorious" one showed flashes of his dynamic striking to back his elite foe up only to get finished via strikes for the first time as a professional in Round 2 following an almost remedial response to Poirier's calf kicks that left McGregor a sitting duck for power shots.

For as much as historians (and podcast hosts, alike) often ponder what the last five years of McGregor's career could have looked like had he not been so inactive while flirting so heavily with boxing and succumbing to the vices of the filthy rich celebrity life, the same might be said one day about his lost 2020.  

Although there's little question that Cerrone, who is currently 0-5 with one no contest in his last six bouts, was the perfect lamb for the matchmaking slaughter of McGregor's comeback (a 40-second TKO), the dismantling was supposed to have kickstarted a return to regular activity for a fighter who had previously benefitted so much from keeping his skills sharp (he fought six times from 2015-16) during the stretch in which he built his legend. 

Unfortunately, McGregor's plans to fight upwards of four times in 2020 were destroyed by the pandemic, along with a brief public war against UFC president Dana White that produced leaked Twitter DMs and the revelation that although McGregor did want to return despite the lack of a live gate caused by the coronavirus, he wanted to do so against hand-picked (I.e. weak) competition that even a promoter not above giving a get-well fight to a returning superstar wasn't willing to sign off on.   

So, was McGregor's eventual loss to Poirier to open 2021 largely the result of yet another 12-month layoff? Again, it's a legitimate (albeit too convenient) excuse. Or was the fight proof that the sport had effectively passed McGregor, and his lack of evolution, by after not taking it seriously enough amid his journey from MMA champion to Page 6 celebrity and household name?  

As far as the questions facing McGregor in this fight, it's the latter that makes his decision to so boldly seek out Poirier for a third time the juiciest, mostly because the risk/reward proposition for McGregor entering this fight is very much real. Should McGregor win, an immediate shot at new lightweight champion Charles Oliveira is his likely reward while a loss almost certainly sends him to the eternal fade of "celebrity fighter" status seeking his final blockbuster paydays against similarly faded stars.  

Despite McGregor flipping the script from the build to their jovial and respect-fueled second fight by trash talking (and returning to calling Poirier a "peahead"), it's simply no longer 2014 when a bully mentality and a big left hand was enough to spur McGregor on. Their first meeting proved to be a seminal fight in Poirier's blue-collar march toward all-time great status as the first-round TKO defeat not only sent him packing back to his preferred weight of 155 pounds, it taught him essential lessons about mental warfare and the Kryptonite of fighting with too much emotion.  

McGregor will need to prove that he used the last six months to make the kind of adaptations to his game that most fighters, even elite ones, simply can't do in such a short period of time. The harsh reality for McGregor could be that his one-note style, even at its reformed best, still might not be good enough to best a fighter like Poirier, who is better than him in just about every aspect of the game.  

It has, admittedly, been a long time since McGregor's "magic" -- that far from scientific blend of other worldly confidence and surging momentum -- has lifted him to a performance the level very few coming in thought was possible, including a one-punch knockout in just 13 seconds against Jose Aldo in 2015 that cemented his name in history.  

Ironically, McGregor returns this weekend to try and prove that his name isn't the only thing he has left.

CBS Sports will be with you all week long with live coverage from Las Vegas for both Morning Kombat and CBS Sports HQ. Keep it locked to this page for constant updates on the fight card, news from the press conferences and availabilities as well as highlights from the weigh-ins. We will also have you covered on fight night with our live blog for round-by-round updates throughout the night.

Who wins Poirier vs. McGregor 3? And which fighter is a must-back? Visit SportsLine now to get detailed top picks on UFC 264, all from the UFC insider who's up nearly $9,500 on MMA picks in the past year, and find out.