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Riding a 17-match unbeaten streak at the Olympics, the Hungarian men's water polo team enters the London Games in search of an unprecedented fourth straight gold medal.

From day one in London, it's not going to be easy.

The Hungarians, who haven't dropped an Olympic match since Sydney 12 years ago, open play at the Summer Games against gold medal-favorite Serbia.

The Serbians, featuring 2010 world player of the year Vanja Udovicic and 2011 player of the year Filip Filipovic, are loaded. They earned the silver medal at the 2011 worlds, then won the European Championship this year.

"Serbia has certainly been the most consistent team over the last three years," said United States coach Terry Schroeder, who helped the Americans to a silver medal in Beijing four years ago. "They've been really the top team and I think they have the most balanced team right now."

Although Serbia stands a tick above the rest of the field, there's a pack of countries with legitimate medal hopes.

Hungary, for one, remains a threat. The traditional powerhouse has won a record nine water polo golds, and brings a star-studded experienced roster to London that includes Zoltan Szecsi, Gergely Kiss, Peter Biros and Tamas Kasas.

"Many said that a third consecutive gold medal was impossible and we achieved that, so a fourth is just as achievable," Szecsi said.

The list of contenders also includes Croatia, another perennial power, and Italy, which topped Serbia to win last year's world title. Montenegro lost 9-8 to the Serbs in the 2012 European Championship final, while Spain finished second at the 2012 FINA World League finals.

Then there's the U.S., which gained valuable experience in Beijing that could pay off this summer.

Four years ago, the Americans beat Serbia 10-5 in the semifinals before falling to Hungary 14-10 in the gold-medal match. They'll have to go through the same heavyweights in London to win the United States' first water polo gold since 1904.

"Gold is what we're capable of, and I know that if we play all of us to our ability, that we're the best team in the world," captain Tony Azevedo said.

On the women's side, the field is wide open, notable as much for who will not be in London as for who will be. The Netherlands, which won the gold medal in Beijing, and Greece, the 2011 world champions, failed to qualify.

The only team that is truly a long shot for a medal is the host nation, Britain. The seven other countries in the field — China, Russia, Hungary, Italy, Spain, Australia and the United States — are all legitimate medal contenders.

The U.S., which won silver four years ago in Beijing, is arguably the favorite with a veteran team led by captain Brenda Villa and Heather Petri, both of whom will be appearing in their fourth Olympics.

Coach Adam Krikorian has five other players from the 2008 squad, as well as a mix of talented youngsters.

"I think our chances look really good," Villa said. "We've been training really hard for the past four years. We're training and not taking anything for granted so we want to come out on top."

The U.S. has medaled in every Olympics since women's water polo was added to the schedule in 2000, but has never won gold. The Americans earned a silver in Sydney, a bronze at the 2004 Athens Games and a silver four years ago in Beijing.

"I think walking away from Beijing with a silver medal was just a lesson that nothing is guaranteed in sport," U.S. goalkeeper Betsey Armstrong said in an email.

"We are constantly asked why our program hasn't been able to 'get it done' when in actuality I think what so many people don't realize if just how difficult it is to win a gold medal — everyone is fighting to be at the top of that podium, and everyone has an equal chance."

The other leading contender is Australia, which won Olympic gold in 2000 and took home bronze four years ago.

Russia and Hungary have placed in the top three of major tournaments in the past year. Spain won the 2012 Olympic qualifying tournament, besting Greece, Hungary and Italy along the way.

It will all be sorted out, for the men and the women, by the second week of August.

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Medal projections:

Men

Gold: Serbia

Silver: Croatia

Bronze: Hungary

Women

Gold: United States

Silver: Australia

Bronze: Spain