Not everyone will have success this summer in the Olympics - and that includes some of the biggest names taking part in London. Here are 10 athletes that could be disappointed at the Games.

His feet were on fire in Beijing back in 2008, setting a world record in the 100-meter race to capture the gold medal and unofficial title of Fastest Man in the World. But at the 2011 World Championships, he was fast in the wrong way. Bolt jumped out of the blocks too early and was eliminated for a false start. So will he get a jump on the competition this time around or get knocked out of the race for jumping the start?

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How can you follow up a record-setting eight gold-medal performance at the Olympics? Phelps hopes it will be with more medals. But this time around, it may not be easy for the swimmer to pick up the hardware. He's struggled in competition against American swimmers, most notably Ryan Lochte and Nathan Adrian, who actually beat Phelps at a meet earlier this year despite ripping his suit during the race.

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In 2004, the U.S. men's team was a bust in Athens, bringing home a disappointing bronze medal. Four years later, the team was redeemed by picking up a gold medal in Beijing. So which team will show up in London? Several gold-medal winners will be returning, but several star players won't be making the trip due to injuries. Will the team be affected by that? We'll have to wait until the medal presentation to find out.

She's near the top of the international leaderboard in heptathlon events and is a former world heptathlon champion. Plus, she will be competing in front of her home country this year. But will that be too much pressure for Ennis to handle? No one would blame the 26-year-old for having some extra nerves with all the home eyes on her, but as a former world champion, she's going to face some tough competition.

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Franklin is already a force to be reckoned with in the pool and her 6-foot-1 frame gives her a distinct advantage over the competition. But she's also only 17 years old. Is the Pasadena, Calif. native prepared to hang tough with the more seasoned veterans she'll battle for medals?

The women are the defending Olympic champions after nabbing a gold medal in 2004 and repeating the feat in 2008. But in 2011, they came in second place at the women's World Cup, losing in the final game to Japan. Many of those players are returning and looking to avenge that loss, but can they come together as a team to get it done?

Wieber has many things working to her advantage. She's the 2011 world champion in both the team and all-around events and picked up three golds at the Pacific Rim Championships this year. With Americans' love of gymnastics events, though, she is going to have more eyes and more pressure than ever before on her shoulders as she competes on the world stage.

Felix picked up a long-coveted gold in Beijing, but it did not come in her showcase event - the 200 meter race, an event where she has won silver the last two Olympics. Anything other than gold will surely be deemed a failure for the 26-year-old this time around. Adding more intrigue to the situation is the major hurdle she faced at the Olympic trials. In the 100m qualifying run, she tied for third place with Jeneba Tarmoh, leading to the final Olympic spot determined by a coin toss/run off. She'll have to perform better than that in London or risk going home without any hardware.

With David Beckham missing the cut for Great Britain's soccer team, fans hopes now fall on the shoulders of veteran midfielder Giggs, who has had his own share of success playing for powerhouse Manchester United. He'll also have to deal with the added pressure of playing in front of the London faithful. But if the partisan crowd doesn't see success early and often in the soccer tournament, Giggs may be the scapegoat for a frustrated local fanbase.

Venus (pictured) has plenty of time to focus on the Olympics after a shocking early exit from Wimbledon at the end of June. Sister Serena suffered a similar fate in May at the French Open. The duo, who won a doubles gold medal together at the 2008 Games in Beijing, will have to put their disappointing grand slam play behind them if they expect to see any kind of Olympic success.

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