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The refusal of four-division champion Canelo Alvarez to rest on the laurels of the success he has already achieved as boxing's simultaneous pound-for-pound king and biggest global draw has made putting any potential limitations in front of him a difficult thing.

Alvarez (56-1-2, 38 KOs) has come a long way throughout a 16-year pro career that began as a teenager in his native Mexico and saw him become a viable pay-per-view star by the age of 23. But as Alvarez, now 31, prepares to make history once more on Saturday in hopes of crowning the first undisputed champion in super middleweight history, it's worth taking a moment to realize just how remarkable Alvarez's evolution has been.  

The reigning WBA, WBO and WBC champion at 168 pounds welcomes IBF titleholder Caleb Plant (21-0, 12 KOs) this weekend inside the MGM Grand Garden Arena. The fact that Alvarez is such a monster betting favorite isn't as much of a surprise as what this fight could represent in the fighter's overall career arc: a full unification of an entire division in less than one year and a final stop before potentially attempting to do the same at 175 pounds.  

"Even harder than getting to the top is staying there," Alvarez said in recent weeks. "That's why I try to get better each and every day. That's what I've been trying to do from my first fight up until now." 

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The Alvarez who suffered his lone pro defeat in 2013 when he dropped a wide decision to Floyd Mayweather in their 152-pound catchweight superfight was a smart boxer and heavy counterpuncher with perceived weaknesses in foot speed. Yet the one who will face Plant on Saturday is nothing short of a 168-pound destroyer, able to walk down his opponents with power, finish them with a counter shot or outthink by relying on his technique.  

Alvarez's dominant success today makes it easy to forget the stretch in time from 2014 to 2016 when the Mexican icon often chose to fight at his preferred weight of 155 pounds -- often playfully dubbed as "Canelo weight" by boxing media -- with his critics wondering whether Alvarez was even big enough to challenge full-sized middleweights like Gennadiy Golovkin.  

So how, exactly, did we get here? A world in which just two years ago, Alvarez dared to be great by moving up to light heavyweight where he knocked defending champion Sergey Kovalev spark out while acting like the bigger puncher throughout? A reality in which Alvarez has openly shared a desire to move back up to 175 pounds to potentially challenge unified champion Artur Beterbiev (16-0, 16 KOs) rather than simply face smaller and more marketable foes for big money? 

"We keep working the same as when we started," Alvarez said. "We have the same vision of being historic and this is what we are here for."

When Freddie Roach, the Hall-of-Fame trainer of eight-division champion Manny Pacquiao, was asked this year what the secret was for Pacquiao's longevity and sustained excellence in his early 40s following such dramatic rise in weight, Roach used words like passion, work ethic and hunger. 

The same spirit can be found in Alvarez, whose recent run up the scales might not be the same as Pacquiao debuting at 106 pounds and winning world titles as high as junior middleweight, yet deserves comparison to the legendary "PacMan" for his ability to carry such profound speed and power with him regardless of the division he's competing at.  

"Sometimes you catch yourself thinking about the road traveled with Canelo," trainer Eddy Reynoso said. "We have almost 17 years working together. The most important thing is he hasn't lost his hunger to keep growing, to keep winning, to keep succeeding at boxing." 

If his trademark merchandise slogan of "No Boxing, No Life" wasn't already enough of an indicator, Alvarez has retained the passion and focus of a challenger climbing the ranks despite the fact that he has already conquered the sport's highest summits. That passion has allowed him to constantly work on his craft and improve his shortcomings.  

While the impact of his perceived slower footwork at junior middleweight has been lessened the more he has risen in weight, it's clear that Alvarez has grown in just about every category from explosion, footwork, defense and targeting the body as possibly the sport's most lethal hooker downstairs. Along the way, Alvarez has become even smarter. He was always patient and poised, but now he's equally deadly at finishing opponents with one perfect punch at the right moment.  

"I'm a complete fighter. I can do various things in the ring," Alvarez said. "I can be aggressive, I can counterpunch, I can move. At the end of the day, I know I have to be a complete fighter. That's what I've learned to be under Eddy Reynoso. 

"The secret to me and Eddy's relationship is our discipline. My mind is so strong and I'm going to use that to my advantage in this fight. I'm a person who likes challenges. I always want to keep learning, learning, learning." 

Alvarez showcased his brilliance perfectly against Callum Smith in their unification bout last December when the native of England chose to spend most of the time pinned to the ropes behind his high guard. Alvarez made the adjustment to target Smith's left arm, which compromised both his jab and defense while creating a torn biceps that needed immediate surgery. 

The truth is that Alvarez has spent most of his career actively seeking out difficult challenges against all different kinds of styles. He famously went against his former promoter's advice by targeting difficult southpaw boxers Austin Trout and Erislandy Lara at junior middleweight and he had no trouble walking down much bigger men years later at 160 and 168 pounds against some of the sport's most violent punchers in Golovkin and Kovalev.  

It's because he has seen it all and conquered nearly everyone he has faced that Alvarez has no doubt he will be able to handle everything that Plant brings to the ring. 

"I know what I need to do and I know a lot about him," Alvarez said. "He's a good fighter but I know my skills. I have faced similar styles to Caleb's against Floyd Mayweather, Erislandy Lara, Austin Trout and [Billy Joe] Saunders. My experience is going to give me the edge in the fight."