SHANGHAI (AP) - Britta Steffen of Germany dropped out of the world championships after swimming the slowest qualifying time in the 100-meter freestyle on Thursday.
The defending champion's time of 54.86 seconds was only good enough for the 16th and last spot in the evening semifinals. It was Steffen's second poor swim in Shanghai, having led off Germany's 400 free relay that earned a bronze last weekend.
"I'm very disappointed, but I have no explanation," she said. "It's not what I expect from myself, but I have to react to this the same way I reacted to the successes."
Steffen said she felt fine in training leading up to the meet and once she arrived in Shanghai, but wasn't able to bring any speed to her races.
Her decision means she won't be part of Germany's team in the 4x100 medley relay on Saturday.
American Tyler Clary easily advanced in the preliminaries of the 200 backstroke, with teammate Ryan Lochte posting the fourth-fastest time.
Clary led the way in 1 minute, 56.32 seconds, putting the United States in good position to defend the title its won eight times in the event, including the past six consecutive world meets.
Clary missed out on the 200 fly final, won by Michael Phelps on Wednesday.
"It was upsetting to see that I got second in my semifinal heat and still didn't make it back because seven guys went faster in the second heat," he said. "Unfortunately, I got caught with my pants down. Definitely not going to make that mistake tonight."
Lochte, the bronze medalist two years ago behind now-retired champion Aaron Peirsol, touched in 1:57.34. Lochte won the title in 2007.
Peter Bernek of Hungary was second at 1:57.23, followed by Stanislav Donets of Russia. Japan's Ryosuke Irie, the silver medalist in 2009, was sixth.
The United States also had the top qualifier in the 200 breaststroke, with Olympic champion Rebecca Soni clocking 2:23.30 and setting herself up for a sweep of the breaststroke events.