Erik Morales has a stern test come March 19 – perhaps the toughest of his career – as he tries to derail the Manny Pacquiao Express in a highly-anticipated junior lightweight showdown in Las Vegas.

The task is daunting for several reasons, the most obvious being that Pacquiao may be the hardest puncher “El Terrible” has ever faced.

“Pac-Man” is also younger, faster and fresher.

And it certainly doesn't help Morales' chances that he is coming off a 12-round decision loss to archrival and former Pacquiao victim Marco Antonio Barrera last November.

But it is not unprecedented for a fighter to score a career-defining victory after a crushing loss. But, to do it, you have to have an iron will and unyielding confidence.

Morales certainly qualifies.

Here are five fighters who scored upsets after a heartbreaking loss.

Pipino Cuevas: The legendary Mexican power puncher was a big underdog going into his 1976 challenge of WBA welterweight champion Angel Espada. Six weeks prior, he had been easily outboxed by welterweight contender Andy “The Hawk” Price, and his title shot was seen as something of a gift. But the “Mexican Assassin” took advantage of the opportunity, stepping up his attack and blitzing the Puerto Rican with his famous left hook in just two rounds. In the process, he became the youngest welterweight champion of all time at age 18. He went on to notch 11 defenses of his WBA 147-pound title over four years, including two more knockouts of the underrated Espada. He lost the title just as he won it – by brutal second round knockout to a young tiger named Thomas Hearns in 1980.

Sugar Ray Leonard: Leonard moped for a while after his 1980 decision loss to legendary lightweight Roberto Duran. It was the biggest welterweight fight of all time, and Leonard had been handily whipped over 15 rounds as he lost his WBC welterweight title. Afterward, he was mocked and taunted by a raging Duran, who denied Sugar the traditional post-fight handshake. All in all, it was a humiliating night for Leonard. But Leonard's mood changed when he heard that Duran was partying hearty and gaining weight at a breakneck pace in celebrating the victory. Leonard and advisor Mike Trainer wisely arranged for an immediate rematch, forcing Duran to quickly switch gears – and shed off weight in record time. Duran somehow made the 147 pounds (from a reported 170 pounds) – then famously gorged himself. On fight night, he was Duran in name only. Leonard, meanwhile, was razor-sharp and bent on revenge. Instead of brawling, he boxed and allowed his amazing reflexes to dominate a dulled Duran. He also gave Duran a dose of his own medicine, mocking and taunting the Panamanian until Duran quit in frustration in the eighth round. As a result, Leonard was a bigger attraction afterwards than he ever was before the Duran loss.

Greg Page: There was a time when Page was one of the more talented fighters in the heavyweight division. He was swift on his feet for a big man, a boxer with quick hands and serious boxing ability. But by the time he challenged WBA champ Gerrie Coetzee in Coetzee's native South Africa in December 1984, Page was considered a has-been. He had lost two fights that year, to Tim Witherspoon and David Bey, and was thought to be a tune-up for the newly-crowned Coetzee. Eight rounds later, Coetzee was lying flat on his back in a packed-but-silent stadium. Page had gone from trial horse to champion and simultaneously realized his vast potential in the time it takes to wash a pair of trunks. He reverted to his lazy form in his next fight, a horrid decision loss to Tony Tubbs, and never capitalized. Page would eventually become one of boxing's sad stories. But his victory over Coetzee, which at least temporarily put him among the heavyweight elite, can never be erased.

Evander Holyfield: Sure, Holyfield had a fight between his first and second brawls with Riddick Bowe. But it almost did more harm than good. He waltzed with Alex Stewart in June 1993 and looked so bad that experts wondered whether he deserved the Bowe rematch five months later. But Holyfield wasn't properly motivated for Stewart, whom he'd already defeated in 1989. Bowe was another matter, and the “Real Deal” entered the rematch with a completely different mindset. He boxed more, and he made the punches that landed count more, as he gained a few pounds of muscle. He also was intent on making Bowe pay for all those rounds in the 1992 original where “Big Daddy” sucker-punched him after the bell. And he did, forcing Bowe to think twice about his illegal tactics. Oh, and “Fan Man” probably didn't hurt, as his annoying 17 minute interference put the brakes on a mounting Bowe attack. In the end, Holyfield won with heart and guts as much as style and smarts, and completely rebooted a sagging career.

Marlon Starling: In July 1988, Starling played the victim in one of the more bizarre welterweight endings in boxing history. After dominating South American challenger Tomas Molinares, Starling was cold-cocked by a scorching right hand a split second after the bell ended the sixth round. Molinares was outrageously declared the new champion (a result which was later changed to a no-contest). To add insult to injury, Starling was interviewed by HBO while still foggy, as he eerily refused to believe what the world had just seen – that he had been flattened. But justice luckily prevailed. Instead of a rematch with Molinares, whom he would have easily defeated, Starling got a shot at the man considered the best 147-pounder in the world, Lloyd Honeyghan. In a masterful boxing display, the “Magic Man” made Honeyghan look like an amateur and pounded him unmercifully in registering a ninth-round TKO. Strangely, Starling had to experience near-career disaster before realizing the highest point of his career.

It takes a good amount of bravery to come back from a devastating defeat. It takes even more to do it against a formidable opponent. We'll see if Morales can do it March 19.