For a fight as incredibly close on paper as Saturday's lightweight title bout headlining UFC 229 in Las Vegas is between Khabib Nurmagomedov and Conor McGregor, everyone from oddsmakers to expert analysts are forced to peer closely to find out what separates them. 

What makes this grudge match between the current and former champion at 155 pounds so unique is that the overwhelming strength of each fighter matches up perfectly with the glaring weakness of the other. If the fight ends early, most believe it will happen via McGregor (21-3) knockout. Should it extend to the third round and beyond, the consensus will be that Nurmagomedov (26-0) has his way on the ground. 

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Yet, from the beginning, Nurmagomedov has been installed as the justifiable betting favorite despite McGregor slowly pulling closer to even during the final days of fight week. The reason for that just might come down to McGregor's inactivity and the fact that this weekend's return to the Octagon will be the brash Irishman's first since 2016. 

The whole thing brings up the topic of ring rust (or maybe a more apt MMA description of "cage rust") and whether that's an old wives tale or a legitimate concern when considering how much the 30-year-old McGregor relies on speed and timing to close distance and knock his opponents out. 

Asked directly about the topic of rust during last month's press conference in New York, McGregor barely paid it any attention when he quickly shot it down with a mixture of arrogance and confidence. 

"We are ready for this," McGregor said. "[I see] domination, his head bouncing off the canvas. He has a glass jaw. I will be prepared for five rounds."

Taking the pulse of experts on the topic produces a mixture of denials that it's even a real thing and more sober takes that it's more a case of the fighter in question and just how active he has been between fights. 

"I think [ring rust] is a myth," UFC Hall of Famer Urijah Faber told CBS Sports on Monday. "I had a big break after I broke my hand against Mike Brown and had surgery. I stayed super active the whole way through. If [McGregor] stayed active in the gym then I don't think there's any doubt that Conor believes in himself and that's the most important thing. On top of that, he took some time to really focus on one area, which is his hands because he had to box the best boxer on the planet, Floyd Mayweather."

Although McGregor initially stepped away from the Octagon for the birth of his first child, Conor McGregor Jr., in May 2017, he quickly entered an intense training camp for his pro boxing debut against Mayweather three months later. Faber believes it's that level of activity, mixed with the audible return of McGregor's hunger in recent interviews, that should offset any fear he won't be the same guy who knocked out Eddie Alvarez two years ago. 

"When you are talking about a guy that never really lost the title and is hungry and spent his off time having maybe the biggest fight of all-time, I don't think you can say is ring rust going to be there," said Faber, who shared with the "In This Corner" podcast just how close he came to fighting McGregor as a late replacement at UFC 196. 

"The question is whether he put his time in grappling because in a two-year period he can make some massive, massive improvements in terms of jiu-jitsu and wrestling with the right training and the right method of attack. The question is has he done that? If he has, he has been a champion for a reason because he must understand how to train properly and I think the odds are in his favor. If he hasn't, the favorite has to be Khabib."

McGregor's head trainer, John Kavanagh, believes it's the intensity of training camp that acts as a purifier of sorts in the removal of any potential rust. 

"I think if your gym environment and how you train in the gym is very separate to how you compete, then for sure there will be ring rust but if you are regularly putting yourself in stressful sparring situations, which is the best we can get in the gym environment, it more resembles competition then," Kavanagh told The MacLife in September.

"So, specifically very much for this training camp, we had a lot of very intense training sessions, sparring sessions, it's done in the environment he's going to compete in. We even had spectators for a lot of the spars, so we're trying to make the training environment as closely mimic the competition environment so there isn't that much of a disconnect between the two of them."

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McGregor will be fighting in the Octagon for the first time in two years on Saturday. Getty Images

Historically, fighters have been publicly shy about admitting that rust was ever a possibility, likely out of a motivational ploy to remove all thoughts of potential weakness. 

If there's an expert on the subject, it's likely former UFC and WEC bantamweight champion Dominick Cruz who has endured through multiple devastating injuries beginning in 2011 which have robbed him of much of his prime. Cruz fought just once (a first-round knockout of Takeya Mizugaki in 2014) over a span of four-plus years yet returned in January 2016 to regain his title via split decision from TJ Dillashaw. 

In 2013, Cruz publicly dismissed ring rust as "something that's brought up to give oddsmakers something to bet on" and believed it to be possible to "work it completely out of your system" in training camp. After his win over Dillashaw, he was just as dismissive. 

"I tried to explain there's no such thing as rust," Cruz said. "How much have I said that? There's only rust if you don't train enough. Remember, ring rust is nothing more than mental weakness."

UFC welterweight champion Tyron Woodley echoed Cruz's thoughts in the buildup to his Sept. 8 dismantling of Darren Till at UFC 228. Woodley shook off a year-long layoff following shoulder surgery and credited his television work with keeping him mentally focused."

"You have to remember that when I won the world title [at UFC 201 in 2016] I hadn't fought in 18 months and I came out and smoked Robbie Lawler in 47 seconds," Woodley told "The Herd" in September. "I don't really believe in ring rust, it's what you do when you are away. What I do at Fox with analyst work and looking at fights allows me to stay sharp." 

A more dramatic example of a fighter facing the potential of extreme ring rust came when MMA legend Royce Gracie returned from just shy of a nine-year gap in 2016 when he fought Ken Shamrock for a third time at Bellator 149. Gracie, who won via first-round TKO at the age of 49, entered the fight without any fear of being rusty largely because of how much his fighting retirement had been filled with teaching and coaching the sport. 

"I've been out of fighting? It makes it sound like I'm sitting at home ... doing nothing," Gracie told MMAJunkie in 2016. "I've been going to the range every day. My drawing is good and fast, I'm on target, I shoot and I don't miss. It doesn't mean I've been going to battle, but it doesn't mean I haven't practiced. It's like a soldier that goes to the range every day and does everything for war. He shoots, he runs, everything is on good. He's just not in battle. That's my case. Now I'm going to go to battle. It doesn't mean I'm fat or out of shape."

The fighter who has been the most honest about the subject in recent years is UFC legend and former two-division champion Georges St-Pierre. His admittance that rust is a real thing largely comes from experience thanks to a 19-month, 586-day absence from the Octagon during the peak of his legendary welterweight title reign. 

St-Pierre returned from injury to defend his title against interim champion Carlos Condit at UFC 154 in 2012 and found himself in a tough fight throughout the late rounds of a unanimous decision win. 

"People talk about ring rust," St-Pierre said afterwards. "I definitely know what it is now. He gave me my toughest fight."

The topic resurfaced when GSP returned from a self-imposed, four-year break from the sport at UFC 217 in 2017 when he successfully challenged Michael Bisping for the middleweight title. During a fan Q&A on Facebook months before his third-round submission win, St-Pierre was realistic about the challenge he was facing. 

"I believe in ring rust. People say there's no such thing, but I believe in ring rust," St-Pierre said. "It will be an issue but I'm a very experienced man. I'm one of the guys that has spent the most time in the octagon in the UFC, maybe the most.

"For me, it will be very important [at] the first second of the fight. That's when I will have to be very aware, very careful. That will be the most dangerous moment for me because when you have ring rust, that's the hardest part of the fight. When you just step in and the fight start, that's where the ring rust comes from, the difficulty of adaptation. But after a few minutes, I will be back to normal."

McGregor faces a similar situation to what the fighters above have been forced to navigate but what separates him in this case is not just the activity of having taken part in a major boxing match but the absence of a serious injury (which produces doubt) to overcome. 

If the lead-up to UFC 229 has taught us anything it's that McGregor is dialed in and as hungry as ever, if his typically bombastic interviews have been any indication. The threat of rust in this case is largely overshadowed by the simple threat of Nurmagomedov's wrestling in what has all the makings to be a classic title fight and, quite possibly, the biggest pay-per-view in the sport's history.