Injury, doping bans, ill-timed losses of form, lack of interest and even a damaged fetlock have left a trail of big-name performers watching the Olympics from the sidelines.
Athletics, the Games's blue riband sport, leads the way in the absentees with its own blue riband event, the men's 100 metres, the biggest loser.
World record holder Tim Montgomery failed to make the U.S. team after finishing seventh in the country's trials in July.
The U.S. system of selecting the first three in its trials has often forced some of the sport's greatest names to miss out but on this occasion there can be few complaints as Olympic champion Maurice Greene won the trial and will be accompanied in Athens by Justin Gatlin and Shawn Crawford.
LIFETIME BAN
Montgomery's loss of form coincided with a long-running doping case which could lead to lifetime ban and has cast a cloud over a whole group of elite US athletes.
Also absent from the sprint is Britain's former European champion Dwain Chambers, who has been banned for doping.
The women's 100 metres has been similarly tarnished, with American world champion Kelli White banned and runner-up Torri Edwards, who inherited the world title, set to follow her compatriot after testing positive for a stimulant.
The likely absence of Edwards could open the door for Marion Jones to defend her 100 metres title. American Jones initially failed to qualify but is travelling to Athens to compete in the long jump and sprint relay.
In the men's 400 metres, world champion Jerome Young failed to qualify and 2000 Olympic silver medallist Alvin Harrison was thrown off the relay squad after a positive test.
In the field events the women's pole vault is unlikely to match the viewing figures of four years ago due to the absence of glamorous Australian Tatiana Grigorieva, whose form has been way off that which earned her a silver medal and an army of admirers in Sydney.
The Olympics remains the ultimate event for athletics but it is not the case for several other sports, leading to a situation where many big names simply opt not to take part.
Lance Armstrong, an Olympian in 1992, 1996 and 2000, has this year instead chosen to spend time with his family after winning an unprecedented sixth successive Tour de France.
Most of the other top professional riders are here although Britain's world time trial champion David Millar was withdrawn after failing a dope test.
Sydney doubles gold medallist Serena Williams was a late withdrawal from the tennis this week, following compatriot and 1992 singles gold medallist Jennifer Capriati, who dropped out with an injury on Tuesday.
NO DREAM TEAM
Baseball will certainly look strange without an American team taking part -- the 2000 champions failed to qualify -- while the days of the "Dream Team" are long gone in basketball and few of the current stars of the NBA have showed any interest in travelling to Europe for the Olympic experience.
Soccer has a special position in the Games, the men's event being for under-23s with three over-age players allowed, but none of the world's top players will be interrupting their club seasons to take part.
In women's soccer, however, the Olympics remains all-important and the qualification failure of Norway, reigning champions and one of the dominant forces in the game for 20 years, is a real shock.
But surely the most frustrated absentee must be Germany's number one world-ranked showjumper Marcus Ehning, who was forced to withdraw this week because his horse -- Sydney and Atlanta team gold medallist For Pleasure -- strained a ligament.
