Olympic boxing preview

SPORTS EXPLAINERS: BOXING

And in this field, there are plenty of prospects who could join them on that list.

Women's sports will break down another barrier in London, when women's boxing becomes a medal event for the first time. Long regarded as a sideshow, women's boxing has built momentum in recent years thanks to a crop of young, talented female fighters who have sprouted up all over the world. Women's boxing still faces many detractors, old-school coaches and trainers who think it has no place in the Olympics. But a strong showing by this field of talented women will go a long way toward silencing those critics.

Rau'shee Warren, USA, Flyweight: Making his U.S. boxing-record third trip to the Olympics, Warren has a sparkling résumé (four-time national champion) with one noticeable hole: an Olympic medal. In 2004, a 17-year-old Warren lost in the first round to eventual gold medalist Zou Shiming from China. In 2008, Warren dropped a close decision to South Korea's Lee Ok-sung. Warren claims to be more settled now, with two kids and a third on the way. And his international experience -- Warren competed in the World Series of Boxing last year -- will be a major plus at the Games.

Lazaro Alvarez, Cuba, Bantamweight: The latest in a long line of skilled fighters coming out of Cuba, Alvarez is the reigning world champion who has beaten up on nearly every top contender in his weight class. Alvarez busted up five top-ten rated opponents at the 2011 worlds before beating down England's Luke Campbell in the finals. An equally dominant performance at the Pan American Games set Alvarez up as the prohibitive favorite in this weight class.

Clemente Russo, Italy, Heavyweight: The 2008 silver medalist is back and ranks among the most experienced competitors in a crowded field. Smallish (5-foot-10), Russo has no problem against bigger men -- he destroyed 6-foot-7 and current undefeated pro prospect Deontay Wilder in 2008 -- and at 29, ranks as one of the most experienced fighters in the field. An Italian policeman by day, Russo comes into the Games hot after winning the 2011 World Series of Boxing heavyweight championship.

Vasyl Lomachenko, Ukraine, Lightweight: Lomachenko is, simply, a star. Fast, flashy with uncanny pop on his punches, Lomachenko won the gold medal at flyweight in the 2008 Olympics and will move up to lightweight in London. At 23, Lomachenko resisted turning pro, where he will likely become a quick sensation, to fight for one more medal. He's easily the most high profile fighter in the tournament.

Claressa Shields, USA, Middleweight: A superstar in the making, the 17-year-old Shields is the youngest U.S. boxer in 40 years. Shields dominated the last calendar year, winning her second straight Junior Olympics, the National PAL tournament and the Women's Continental Championships. On the way, Shields routed Mary Spencer, the iconic middleweight queen, which firmly placed her among women's boxing's elite. Because of the limited number of weight classes, Shields, a natural 154-pounder, fights at 165. But her blend of power and skill makes her a strong gold-medal favorite

Mary Spencer, Canada, Middleweight: The aforementioned Spencer took the loss to Shields in April, but that hardly diminishes her credentials. A three-time world champion, eight-time national champion and 2011 Pan American Games champion, Spencer, 27, ranks as one of the most accomplished women boxers in history. Spencer enters the game riding a two-fight losing streak, but she still stands as the best chance to end Canada's 24-year gold-medal drought in boxing.

Ren Cancan, China, Flyweight: Last May Ren, 24, became the first Chinese woman to win three straight world titles. Ren knocked off U.S. medal hopeful Marlen Esparza in May, using her superior height (5-foot-6) and reach as tactical weapons. Observers cite her footwork and speed as her greatest strengths. "The Chinese have done a good job playing to what the judges look for," said Christy Halbert, chair of USA Boxing's women's task force. "She's long with her punches and very active."

Savannah Marshall, Great Britain, Middleweight: Marshall's "whoa" moment came in May, when she upset Shields en route to a gold medal at the world championships, becoming Great Britain's first amateur world boxing champion. The 21-year old Marshall is raw -- she started boxing at 12 -- but has already shown tremendous polish. A thinking woman's fighter, Marshall operates behind her jab, builds a lead, then protects it the rest of the fight. It isn't pretty, but it sure has been effective.

Shields is the U.S. team's top dog, a bona fide superstar in the making who, despite fighting in a crowded weight class, will be a gold-medal favorite. Esparza is a stylish flyweight -- she admits she primps herself before fights as she would going on a date and has an endorsement deal with Cover Girl -- who fights with a slick style. She has won five straight national titles and a owns a bronze medal from the 2006 World Championships. Queen Underwood goes to London with a high profile, but USA Boxing sources have questioned her commitment in the last year. Underwood needed an exemption just to qualify for the Olympics.

Warren is the U.S.' elder statesman, and according to USA officials has been more focused than ever the last few months. Michael Hunter is a flashy heavyweight -- he wears an emerald-green robe to the ring -- who has sparred with heavyweight champion Wladimir Klitschko. The son of former pro Mike "The Bounty" Hunter, Hunter has thrived since dropping down from super heavyweight in 2008. Hunter was suspended for three months and stripped of his gold medal from the 2011 trials after testing positive for marijuana, but bounced back to win a national championship in March. Lightweight Jose Ramirez is just 19 but experienced with 143 amateur wins.

Claressa Shields vs. Mary Spencer: If there is one matchup everyone is looking forward to, it's this. Shields knocked Spencer off the middleweight mountaintop when she blew her out in the finals of the American Boxing Confederation's Women's Elite Continental Championships. Spencer has vowed to avenge that loss, while Shields, in an interview with SI.com, said she plans to "beat her ass again." It's a classic old generation-new generation rivalry, with Shields trying to stake her claim to division supremacy and Spencer trying to prove she has more fight left in her.

Everyone, really: Amateur boxing is changing, with traditional superpowers like Cuba and the U.S. giving way to stars from rising countries like Kazakhstan, China, Ukraine, Azerbaijan, even India. The beauty of the 2012 competition is that it is wide open, with few true favorites in the field.

Men

The computerized scoring system -- where a fighter gets points strictly for punches landed -- has been roundly criticized, and for good reason. It's hardly an accurate barometer for who is winning a fight, with pitter-patter punching being encouraged and the strong possibility of fighters building an early lead and then running and blocking for the remaining rounds to win. "It's a joke," USA Boxing adviser Freddie Roach said. "It's why many of the best amateurs these days are not turning into the best pros." The system will be scrapped after this summer in favor of a pro-style scoring system, but for one more year fighters will be at the mercy of scoring that doesn't always favor the better fighter.

Women

With only three weight classes (112, 132 and 165 pounds), many of the 36 women in the field have been forced to bulk up (Shields, a natural 154-pounder, will fight in the 165-pound class) or slim down (Underwood, a natural 140-pounder, will fight at 135) just to compete. That could lead to some interesting size matchups. The goal, according to international boxing officials, is to ultimately increase the number of weight classes to 10, which would hopefully encourage more women to participate.

Aug. 9: Women's flyweight, lightweight, middleweight

Aug. 11: Men's light flyweight, bantamweight, light welterweight, middleweight, heavyweight

Aug. 12: Men's flyweight, lightweight, welterweight, light heavyweight, super heavyweight