It’s not everyday that you see a fight previously regarded as competitive turn into a massacre — such as last Saturday’s Joe Calzaghe-Jeff Lacy surprise.

But it happens. It happens a lot.

Here are a few fights that were pick ’em affairs — some of them superfight-style matchups — going in, only to swing in favor of a surprise landslide winner.

And, in some cases, the winner was an underdog.

• Salvador Sanchez TKO 8 Wilfredo Gomez (Aug. 21, 1981, Las Vegas): Going in, Gomez appeared invincible. He was the undefeated challenger from Puerto Rico, a power puncher who had notched 13 defenses of his 122-pound title. “Bazooka” had so cleaned out his division that he stepped up to challenge WBC champ Sanchez at 126 pounds. A smooth counterpuncher from Mexico, Sanchez had reigned for a year-and-a-half after upsetting the popular Danny “Little Red” Lopez in early-1980. But it was Gomez who entered as the favorite, based on his power: He had knocked out 32 straight opponents since being held to a draw in his pro debut, and some figured he was the best pound-for-pound fighter in boxing. He was the complete package: He possessed boxing ability, knew his way around a boxing ring, and that punch. Wow, that punch. Gomez didn’t just beat people. He destroyed them. All-time great Carlos Zarate was among his victims, as was talented up-and-comer Derrik Holmes. It didn’t matter who Gomez fought. He owned them. Meanwhile, Sanchez, as skilled as he was, often appeared vulnerable against the likes of Patrick Ford (W 15) and Juan LaPorte (W 15). His quality was undeniable, but there were lapses, and he often seemed to fight to the level of his competition. Going in, it appeared to be an uphill battle for the defending titlist. Once in the ring, however, a motivated, confident Sanchez stormed out of his corner and blitzed Gomez. He dropped him with a left hook early in the first round, and gave the challenger a fierce working-over. Gomez showed guts the rest of the way in surviving, and the middle rounds were entertaining. But Sanchez was bigger, stronger and, ultimately, better. The exhausted, battered Puerto Rican finally succumbed in the eighth round. Sanchez did it much the way Calzaghe did it to Lacy: By overwhelming his opponent with volume and speed. The end came with Gomez nearly being knocked headfirst into press row. Afterwards, he was a mess — his right eye roughly resembled a softball, and the left eye wasn’t much better. Afterward, Sanchez celebrated with his countrymen. And while Gomez rebounded to win titles in two more divisions, he was overwhelmed by Sanchez. And, on a hot summer night in Sin City, there was little doubt as to the identity of the world’s best featherweight.

• Donald Curry KO 2 Milton McCrory (Dec. 6, 1985, Las Vegas): This one, dubbed “The Toss-Up”, pitted a pair of undefeated champions. Curry was the WBA/IBF champ from Fort Worth, Texas. He had won the vacant WBA crown in 1983, with a so-so decision over the limited-but-determined Jun Sok Hwang. However, the “Cobra” had inched his way closer to superstardom with a string of outstanding victories over top-flight opposition, including Marlon Starling (W 15), Nino LaRocca (KO 6) and Colin Jones (KO 4). Going in, he was a solid favorite to defeat his counterpart from Detroit, McCrory. McCrory, known as the “Iceman”, was the virtual twin of Kronk stablemate Thomas Hearns. He was 6-foot-1, long and lean, and possessed a big punch — though not nearly as harmful as the “Hitman’s.” And he actually was more impressive early in his career than late, when his power seemed to disappear once the quality of opposition improved. McCrory often struggled in decisions over the likes of Jones (two hard-fought, decision victories). Even with some of McCrory’s sub-par performances, however, his pairing with Curry was intriguing. It would crown the first undisputed 147-pound king since Sugar Ray Leonard knocked out Hearns in that classic “Showdown” three years prior. Once the ring clanged, however, it was no Leonard-Hearns. It was a demolition. Curry was physically superior to McCrory in every way — strength, punching power and speed. He took the fight to McCrory early, and, in the second round, flattened him with a gorgeous left hook. McCrory got up, only to be dropped again with a right hand. This time, he didn’t get up. And Curry zoomed his way up the pound-for-pound lists. For a little while, at least.

• Michael Nunn KO 1 Sumbu Kalambay (March 25, 1989, Las Vegas): Though IBF middleweight champ “Second To” Nunn was thought to be Leonard’s heir apparent, he was surely going to get a tough fight from Zambia’s talented Kalambay, the WBA 160-pound champion. Or so the experts thought. Nunn, a southpaw with boxing skill, seemed to have everything. And he was coming off a 1988 in which he was named “The Ring” magazine “Fighter of the Year.” If there was a criticism, however, it was that the Davenport-turned-Los Angeles resident lacked a punch. Instead of blowing opponents out, he specialized in overwhelming them with speed and ability. But, without a punch, experts wondered how he could be a star in the mold of Leonard, despite coming off wins over the top -notch Frank Tate (KO 9) and Juan Roldan (KO 8). In the other corner, Kalambay’s claim to fame was that he had upset future Hall-of-Famer Mike McCallum in early ‘88, making believers out of most of the American naysayers. And, before that, he had defeated Iran Barkley (W 15) and Herol Graham (W 12). He was smooth and crafty, and his experience figured to trouble the youthful, comparatively green Nunn. Then, seconds into round one, the prefight skinny was proven to be myth. Boom! Kalambay leaned in after an exchange, and Nunn fired a perfect left hand counter that paralyzed the WBA champ for an instant, before sending him sailing to the deck. At ringside, they said the punch sounded like a shotgun blast. Kalambay tried to get up on instinct, but was useless. With one big punch, Nunn went from superstar-in-waiting to superstar. Kind of. As HBO’s blow-by-blow man Jim Lampley exclaimed, “….and Michael Nunn answers a lot of questions about his punching power.” As it turned out, it was an aberration. Nunn wasn’t a puncher, and he never really became a star — mostly because of his ho-hum attitude. He was the pugilistic cake that didn’t rise. Today, he sits in a jail cell. But he’ll always have that one moment when he stiffened Kalambay, and was the talk of boxing.

• Roy Jones Jr. W 12 James Toney (Nov. 18, 1994, Las Vegas): Wow, did this fight look like the real deal going in. There was Toney, the two-time champion from Ann Arbor, Mich., whose bite was every bit as effective as his bark. Whether he sat back and boxed — as he did in victories over Merqui Sosa (W 12) and Mike McCallum (W 12) — or rumbled without pause — the McCallum original (D 12), Nunn (KO 11) — he was equally effective. His counterpunching ability was peerless. The boxing ring was his living room, and he seemingly had mastered every nuance, every angle, of the fight game. Besides that, he had a nasty attitude — daring people to test him. Across the blue canvas was Jones, perhaps one of the most physically gifted fighters in boxing history. His speed was so phenomenal that most of his opponents were demoralized by the end of the first round. But, besides that, he could punch. Boy could he punch. The left hook to the liver that buried poor Glen Wolfe was the stuff of legend. And the volley of hydrogen bombs that flattened Jorge Vaca was one of the more impressive offensive assaults of the 1990s. So, the stage was set: Toney’s blue-collar, bring-your-lunch-pail to work, bad-ass persona, vs. Jones’ amazing natural ability. The “Uncivil War” couldn’t miss, right? It missed, if only because Jones was so much better. Jones dominated Toney from the early seconds of round one to the waning moments of round 12. It had become so routine that the crowd was bored stiff by the end of it. In every way imaginable, Jones had mastered Toney — keeping him at long range and controlling the exchanges with his hand and foot speed. Toney could only fire a desperate counter punch and pray. He had never seen the kind of blazing quickness that Jones possessed. In the fourth round, Jones was so in control that he dropped his hands and mocked Toney. “Lights Out” responded by dropping his gloves, and by the time hecould react, Jones had already slapped him with a left hook.  Toney fell back awkwardly — and embarrassingly — and dropped on his butt in a corner. That sequence served as a microcosm to the fight. Both went on to achieve further success. But no one ever called for a rematch. The better fighter was obvious.