Natalie Coughlin was considered one of the top contenders for the most overall medals entering the World Swimming Championships.
Midway through the competition, the American star is just struggling to get out of bed with a fever.
After failing to qualify for the 100m backstroke -- her favorite event -- in Monday's heats, the University of California swimmer did the same yesterday in the 100m freestyle heats.
She's among the world's best in both events.
Coughlin, 20, swam a time of 56.98 seconds yesterday. That put her in 31st position after 12 heats with only the top 16 swimmers qualifying for the semifinals.
"That's the first I've been out of bed for the past two days and the first time in the water," she said. ``I'm pretty happy with how it went. I really was unsure how the race was going to turn out. I'm pretty happy with it.
"Hopefully things will look up and in the next few days I'll get better," Coughlin said.
Asked if she was going back to bed, she replied: "Yes."
American team officials said Coughlin was unlikely to swim in the 800m freestyle relay later Thursday.
"She's just sick. At this point we believe it's a viral illness," said Dr. Scott Rodeo, US team physician.
Coughlin, billed as the best US female swimmer since Tracy Caulkins, did win gold as a member of the US 400m freestyle relay team on Sunday, the first day of competition in the Palau St. Jordi pool.
Hanna-Maria Seppala of Finland led the 100m freestyle qualifying yesterday in 54.82 and Coughlin's teammate Jenny Thompson -- an eight-time Olympic champion -- was just 0.01 seconds back with the second-fastest time of 54.83.
World record-holder Inge De Bruijn of the Netherlands is not competing in the 100 free.
In 200 individual medley qualifying, rising American star Michael Phelps led in 1:59.71, nearly two seconds off his world-record time of 1:57.94 set late last month. George Bovell of Trinidad was second-fastest in 2:00.94 and Italy's Massimiliano Rosolino was third in 2:01.24.
Australian swimming superstar Ian Thorpe just barely qualified for the semifinals in 2:02.54, tied for 14th position with the top 16 reaching the semifinals.
The 200m IM is the only event that Phelps and Thorpe, considered the world's top two swimmers, face off in.
Thorpe has won three golds in the championships thus far to Phelps' one gold and one silver.
Later Thursday, finals were scheduled for the men's 100m freestyle and 200 breaststroke and the women's 50m backstroke, 200m butterfly and 800m freestyle relay.
The American relay team of Rhiannon Jeffrey, Rachel Komisarz, Gabrielle Rose and Margaret Hoelzer posted the fastest time in the 800m freestyle qualifying.
China was second fastest in 8:04.97 and host Spain was third in 8:05.52.
Favorite Grant Hackett of Australia led the 800m freestyle heats in 7:55.15, ahead of his two main challengers Graeme Smith of Britain (7:58.66) and Larsen Jensen of the US (7:59.18).
In men's 100m backstroke qualifying, Aaron Peirsol of the US led in 1:57.28, more than two seconds off his world-record time of 1:55.15 set last year. Australia's Matthew Welsh was second fastest in 1:58.26 and Arkady Vyatchanin was third quickest in 1:59.18.
Austrian Mirna Jukic led the 200 breaststroke heats in 2:27.91, just ahead of American Amanda Beard (2:27.95). Qi Hui of China, who owns the world record of 2:22.99, was fifth fastest in 2:28.74.