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On Saturday night at MGM Grand Garden Arena in Las Vegas, Saul "Canelo" Alvarez will attempt a massive jump in weight to take on the larger, heavy-hitting Sergey Kovalev for the WBO light heavyweight title. The fight is Canelo's attempt to win gold in a fourth weight class and his debut at light heavyweight, having topped out previously at super middleweight where he defeated Rocky Fielding.

Kovalev (34-3-1, 29 KOs) is no Fielding. Kovalev is in the late stages of his career but still brings serious power to the ring. And Canelo (52-1-2, 35 KOs) will be at a size and strength disadvantage no matter how much he bulks up to move from his true home at 160 pounds to the 175-pound light heavyweight division. There's a historical precedent for this kind of big jump in weight to chase glory and gold. If the Las Vegas odds are any indicator, Canelo is expected to follow in the footsteps of some of those all-time greats in accomplishing his goal while putting himself at great risk.

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Let's take a look at three times fighters made a jump and scored legendary wins.

Roy Jones Jr. vs. John Ruiz -- March 1, 2003 

Aside from a single career stumble when he'd hit Montell Griffin after a knockdown, resulting in a disqualification loss, Roy Jones Jr. had been the picture of perfection in the ring when he decided to make the jump to heavyweight. Jones had won titles at middleweight and super middleweight before a lengthy reign at light heavyweight that included a stint as the undisputed champion. As his fights became less compelling because of a lack of interesting opponents at 175, Jones set the goal of being the first former middleweight champion to win heavyweight gold since Bob Fitzsimmons in 1897.

In Ruiz, he had the perfect dance partner. Ruiz had captured the WBA heavyweight belt against Evander Holyfield -- whom he'd lost to one fight prior. He defended the title twice, drawing in a rubber match with Holyfield and defeating Kirk Johnson by disqualification. While he was a talented boxer, he was known for putting on boring fights.

The fight went entirely Jones' way, in large part because of a speed advantage enjoyed by the smaller man. Jones didn't top 200 pounds coming into the the fight while Ruiz was taller by four inches and heavier by at least 25 pound. Ruiz had trouble keeping up with Jones and by the end of the fight, his face was a mangled, bloody mess as Jones took obvious, wide scorecards to become heavyweight champ.

Michael Spinks vs. Larry Holmes -- Sept. 21, 1985

Prior to Jones, the only light heavyweight to jump to heavyweight and win a title in his first fight was Michael Spinks. Spinks accomplished this feat by defeating Larry Holmes, who was a 5-to-1 favorite. Holmes was older and slightly declined from his peak, but he'd held the heavyweight title for more than 20 fights and was seeking to equal Rocky Marciano's record of 49-0 when he stepped in against Spinks.

Spinks brought in a nutritionist to put on weight to make the jump and face Holmes. "I'm eating nuts, bolts, screws, razor blades and sledgehammers," he said ahead of the fight. "I can eat as much as I want, but only what Mackie says I can eat." In an era where weightlifting was also frowned upon by purists, Spinks hit the weights to build his strength. "I don't care what he eats or what he lifts," Holmes said. "When he gets into the ring he's gonna be smaller, and he's gonna be fearful."

Despite entering the ring with a chest cold, Spinks outworked Holmes. As with Jones' defeat of Ruiz, the smaller man's speed was too much to handle for the natural heavyweight. As the heavyweight champ rose from his stool for Round 15, his corner implored him. "It's the last goddam round," Richie Giachetti said. "There's no tomorrow. You got to let it all hang out." As it turned out, the fight was hanging in the balance, even on two judges' scorecards heading into the final round. The action in the round was all Spinks, however, and the smaller man pulled off the tremendous upset.

Ray Leonard vs. Marvin Hagler -- April 6, 1987

Coming out of a near three-year retirement because of a detached retina to fight his largest opponent to date, a middleweight wrecking ball, it's no wonder "Sugar" Ray Leonard was the underdog when he fought "Marvelous" Marvin Hagler. The fight was one fans had long wanted to see, but seemed ill-advised at the time, with blindness a real possibility for Leonard. It was while watching a Hagler fight from ringside that Leonard made the decision to fight once again.

"I was at ringside sitting with Michael J. Fox," Leonard said of the decision. "We were sitting there having a few beers, and I'm watching John 'The Beast' Mugabi outbox Hagler. Of all people, John 'The Beast' Mugabi. Now, I had had a few beers, and I said, 'Michael, Michael, I can beat Hagler.' And he said, 'Ray, do you want another beer?' I said, 'Yes I do, but I can beat Hagler.'"

Hagler had scored 52 knockouts in his 62 career wins but did appear to be slowing down a bit in his skills heading into the Leonard fight. What followed was one of the most controversial decisions in boxing history. After 15 rounds of fantastic back-and-forth action, Leonard was awarded a split decision victory. While the 115-113 official scorecards both ways were defensible, judge Jose Guerra turned in a card of 118-110, leading some fans to claim the fight wasn't entirely on the level for more than 30 years. It was one of Leonard's finest performances in an amazing career, however, and he has since admitted to the level of fear he felt heading into the fight.

"I know something that I'm sure you guys are not privy to and that is that I was so fricking scared," Leonard said in an Instagram video in 2017. "As I walked towards that ring and then when I got to the ring, I'm moving around and looking confident and what have you, but inside my head and inside my heart, there was still a little doubt.

"Not that much but it speaks volumes, it speaks heavy."

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