Nine years. 

Featherweight champion Jose Aldo hasn't lost in nearly nine years. He's riding an 18-fight win streak and boasts a career record of 25-1. Along the way he's beaten the likes of Cub Swanson, Urijah Faber, Kenny Florian, Frankie Edgar and Chad Mendes twice. 

Mendes threw everything he had and then some at the champ in their rematch, and Fight of the Year candidate, at UFC 179. A few even thought Mendes won the fight. 

But all of it wasn't enough to keep the Aldo from winning, 49-46, on all three judges' scorecards. Pushed harder than he ever has been, Aldo rose to the occasion, outstriking Mendes by a 3-2 margin to capture four out of the five rounds. 

UFC welterweight Matt Brown was so impressed with Aldo's performance he took to Twitter to state he has a strong case for being MMA's pound-for-pound best fighter. 

Aldo impresses again. Has a strong case for #1 p4p #UFC178 @assassinscreed

— Matt Brown (@IamTheImmortal) October 26, 2014

After the fight, MMA colleague Chad Dundas shared some thoughts on Aldo with me:

"In a way, I find Aldo kind of frustrating to watch because I always feel like he has an additional gear he can take it to, if he needs to do it. I keep thinking back to the last minute or so in the first (before the illegal punch) after Mendes poked Aldo in the eye (the first time) and Aldo came out of the restart looking as terrifying as anyone on the planet. That's how I remember him always fighting in the WEC. Yet in the UFC he seems to kind of turn it on and off."

Perhaps that lies at the heart of why Aldo—barring a Jon Jones loss—will never wrest away the title of pound-for-pound best from the light heavyweight champ. While Aldo has been every bit the killer—in the sporting sense—for much of his UFC reign, it's felt like he's rarely revved it while in fifth gear, seeming content to mostly cruise in third. 

That didn't seem like the case during his reign of terror in the WEC.

Aldo went 8-0 under that promotion's banner, with seven of those wins coming by way of T(KO), the highlight a double flying knee combo he tattooed across Cub Swanson's dome. His lone decision win came against Faber; Aldo pasted so many kicks to Faber's legs his cornerman chose to carry him back to the stool after the third round. A post-fight photo of Faber's leg is both hard to look at and hard to look away from.

In the UFC, Aldo has gone 7-0, with only two of those wins coming by way of T(KO).

One came via a perfectly placed spinning knee to the skull of Mendes in their first fight (amidst some controversy as Aldo grabbed the cage prior to that to maintain his position). The other came against Chan Sung Jung in a fight that saw Aldo injure his foot in the first round—thus greatly slowing his attack—while Jung separated his shoulder in the fourth round, allowing Aldo to swoop in on a mostly defenseless victim. 

There are at least two theories—both carry at least some weight—as to why Aldo was able to finish all but one of his opponents in the WEC while only finishing two so far in the UFC. The first being that the competition increased significantly once he stepped inside the Octagon.

That very well may be true. 

Five of his eight victims inside the WEC did end up competing for the UFC—Urijah Faber, Cub Swanson, Mike Brown, Manny Gamburyan and Jonathan Brookins. Those five have gone a combined 20-12-1 inside the Octagon. 

Looking as this UFC foes, no one would argue that Chad Mendes and Frankie Edgar are not his two toughest. Aldo finished Mendes in their first fight and at UFC 179 landed a whopping 122 significant strikes. Mendes, it would seem, was not to be finished on that night. And Frankie Edgar. He's never been finished by anyone. 

Alas, there is no formula that can definitively calculate if Aldo's UFC competition has been vastly superior to that of the WEC. 

Aldo's other three UFC victims are Mark Hominick, Kenny Florian and Ricardo Lamas. All of them have been finished by lesser fighters than Aldo with the exception of perhaps Florian, who lost to an in-his-prime B.J. Penn at lightweight and Diego Sanchez at the The Ultimate Fighter 1 finale (which was contested at middleweight). 

Past the strength-of-competition debate, the other theory is that of cage size. The WEC featured a 25-foot cage, while the UFC typically operates with a 30-foot one. It's hard to fully measure what that extra five feet means in terms of how it changes the dynamics of a fight.

Luke Thomas of MMAFighting.com wrote a fascinating piece on Aldo in general and had a section on how the larger cage has affected his style (note: Thomas believes that Aldo is in fact facing "significantly tougher opposition" in the UFC). 

There is a conventional opinion that Aldo's deadliness has declined since moving from the WEC to the UFC. There might be some validity to that. It's true he's facing significantly tougher opposition, which impacts his ability to be more openly offensive. It's also true as Aldo matures, he makes himself less open to counterattack.

What few consider, though, is Aldo's deft use of open spaces. In the WEC, that was limited due to the smaller cage. In the UFC, he has an incredible amount of space to work with against charging opposition. If you try to walk him down, he circles out at long angles. If you press him against the fence (itself, a difficult task), he quickly creates separation and scrambles away. If you try to blitz him, he uses huge swathes of the Octagon to thwart the attack.

From there, he resets the fight. Aldo's UFC fights, in fact, are filled with resets. He constantly uses negative space to stymie any attack or forward progress from his opponents, only to then use that same space to reset the fight on his terms: standing across from him, being picked off by leg kicks, jabs and hooks to the body. That's not the sum total of his offense. His has good takedowns from the clinch and loves opening up with combinations when he gets opponents to put their backs along the cage. But the visual of Aldo posing off against weary fighters inching their way towards him is more than just a little common. It's arguably the centerpiece of his offense. It's his fight on his terms. He can use his explosive power to hurt in bursts while moving away from everything else thrown at him.

So the larger cage that is the Octagon has allowed—or forced—Aldo to paint with a broader brushstroke. He's not fighting in a phone booth, and it has become less of a knife fight. And perhaps he has developed less of a "kill or be killed in a hurry" mindset. In the WEC all of his seven finishes came in eight-and-a-half minutes or less. 

Thomas points out that Aldo has made himself less open to counterattack. Perhaps that's because he knows he is facing tougher competition and has elected to fight smarter versus more aggressively. 

Be it overall tougher competition, and/or having to operate in a bigger space, for many watching, the optics of Aldo have changed. Trying to parse out whether it's external factors, or if there has been an internal shift with Aldo—calculated or otherwise—is ultimately an exercise in futility. 

The net effect, though, of Aldo going from finishing almost all of his fights to only finishing a few, has negatively impacted his image.

And it is not all that different from what former welterweight champ George St-Pierre went through.

He went from being known as the guy throwing superman punches to not being able to finish a fight (from Thiago Alves to Johny Hendricks he went over four years without a finish). It's why Anderson Silva won out with most in the debate over who the pound-for-pound best was...even when many thought St-Pierre had faced tougher overall competition. Silva finished fights, often in dramatic fashion.

Comparatively, Aldo is St-Pierre and Jones is Silva (not that anyone thinks Aldo has faced tougher competition than Jones, which may ultimately be the deciding factor in their battle over No. 1).

And it's not just that Jones has nine finishes in his 14 UFC victories, it's who he's finished and how he's finished them. Who can forget the sound of Brandon Vera's orbital bone breaking via an over-the-top elbow strike or the sight of Machida in a pile after a standing guillotine choke? Watching Shogun Rua being pounded on, over and over, and in every imaginable way, until his fighting spirit could take no more. 

Jones and Aldo both write violent poetry inside the cage. Both are artists of destruction wielding creativity like that of Picasso or Mozart.

But while Jones was pounding Rua into oblivion, Aldo was gassing against Hominick. When Machida was lying lifeless on the canvas, Florian was holding his own. Jones cut through Chael Sonnen like sliced butter just two months after some actually thought Edgar beat Aldo three rounds to two. 

So what does Jose Aldo need to do to pass Jon Jones as MMA's pound-for-pound best?

Barring a Jones loss, it simply may not be possible. Jones is champ of the UFC's glamour division. He's beaten a who's who of MMA legends and is a lightning rod outside of the cage while Aldo's mostly been mute. 

To start with, though, he needs to own his fifth gear. He needs to remember that he, more than anyone, is Neo in The Matrix. He needs to go out there and remind us of the scarfaced killer he was in the WEC. Quite simply, he is going to have start wrecking his competition in a way that Jones has been doing for years. 

And if he doesn't, if he can't, if he chooses not to for whatever reason...well, that's more than OK.

Maybe he's matured past the berserker that he once was and now prefers a more measured and tactical approach, taking what the fight gives him rather than feeling the need to prove himself. Less checkers and more chess. 

Don't be surprised if we see Jones morph into more of that over the years.  

Beyond the conjecture, past the chirping from fans and pundits alike, Aldo will go down as one of the all-time great mixed martial artists, alongside Jones and Silva. 

Those two have been called mercurial. Aldo has become an enigma in his own right.