Shanghai: Michael Phelps` rocky season took another turn for the worse on Tuesday when the 14-time Olympic gold medallist was stunned in the world championships 200m freestyle by US team-mate Ryan Lochte.
Phelps led over the first 100m until Lochte surged from third place to claim a narrow win in 1min 44.44sec, with defending champion Paul Biedermann of Germany third.
The result means Phelps, the Olympic champion and former world record-holder in the event, fails to regain the crown he lost to supersuit-wearing Biedermann two years ago. South Korea`s Park Tae-Hwan was fourth.
"I think that if I was on the other side of the pool that race could have been played a little different. I think I woke him up in the first 100 and he went with it," Phelps said.
"I can`t complain. I`m bummed I didn`t win. But at the same time with what we`ve done over the last 18 months, I`m over a second faster than I was last year and a second-and-a-half off my best time in a suit."
Phelps remains on course for a possible five gold medals in Shanghai, which would match his haul in Rome two years ago.
He claimed bronze on Sunday when the United States suffered a rare defeat in the 4x100m freestyle relay.
Meanwhile Camille Lacourt and Jeremy Stravius bizarrely became France`s first male world champions -- in the same race. Both swimmers won the 100m backstroke in 52.76, in only the second such incident in world championships history.
The unusual result echoes 2007`s 100m freestyle world title race when Italy`s Filippo Magnini and Brent Hayden of Canada both topped the podium with identical times of 48.43
In other results, America`s Rebecca Soni defended her 100m breaststroke world crown ahead of Olympic champion Leisel Jones of Australia and Asian title-holder Ji Liping of China.
And Zhao Jing secured China`s second swimming gold in another upset win when she beat Olympic title-holder Natalie Coughlin into third place in the women`s 100m backstroke.
Zhao finished in 59.05sec, just one-hundredth of a second faster than 2009 silver-medallist Anastasia Zueva of Russia.
The win for Zhao, 20, follows 15-year-old Ye Shiwen`s stunning triumph for China in the women`s 200m individual medley, when she shocked the reigning world and Olympic champions on Monday.
Also on Tuesday, Danish 800m world champion Lotte Friis built an early lead and stayed ahead to win the women`s 1500m by six seconds from American world record-holder Kate Ziegler and China`s Li Xuanxu.
But most attention focused on Phelps, who has said he is into the final year of his career as he builds towards London 2012, where he will aim to add to his 14 Olympic titles -- including a record-breaking eight in Beijing.
The 26-year-old Baltimore Bullet admits he has struggled for motivation since the 2008 Games, and has slumped to a series of shock defeats this season. But he says he is back on track and training well under coach Bob Bowman.
He arrived in Shanghai with 22 world titles but suffered a disappointing start when the United States finished third in the 4x100m relay, ending an unbeaten world and Olympic streak stretching back to Athens 2004.
In 2009, Biedermann beat Phelps by a wide margin in the 200m freestyle and shattered his world record with a time of 1:42.00. The German was wearing one of the high-tech, polyurethane swimsuits that are now banned.