Chris Hoy was victorious in Copenhagen last year
Britain's Chris Hoy failed in his bid to defend his men's kilometre title on the opening day of the World Track Cycling Championships in Stuttgart.
Hoy could only finish fourth behind home favourite Stefan Nimke who gave the hosts the perfect start.
Shane Kelly of Australia came second to take the silver while former four-time world champion Arnaud Tournant of France won the bronze.
The result was a serious blow to the Olympic hopes of British cycling as Hoy and team-mates Jason Queally and Jamie Staff were tipped to do much better.
Hoy's time was quicker than the performance which won gold for Scotland at the Commonwealth Games last summer and earned him the world title in Denmark.
Queally, who won gold in Sydney in 2000, and Staff completed an all-British podium at the Commonwealth Games behind Hoy.
Queally, who finished a disappointing ninth in Stuttgart, may need to improve rapidly as he is not guaranteed a chance to defend his Olympic title in Athens despite winning Britain's first medal at the Sydney Games.
Britain can only enter two riders in the time-trial and the Lancastrian could face a showdown against Staff at next month's Olympic trials at the Manchester velodrome.
He was second best to Staff on Wednesday, with the former BMX world champion coming seventh.
Third straight gold for Slusareva
Meanwhile, there was better news for Hoy's teammate Bradley Wiggins who posted the fastest time in qualifying for the men's individual pursuit.
Wiggins completed the 4,000m (2.485-mile) event in four minutes 17.342 seconds to advance to the first round.
Australian Luke Roberts was second fastest, booking his first-round berth in 4:21.822, while Spain's Sergi Escobar Roure finished third to advance in 4:21.941.
Britain's Paul Manning was fourth in 4:22.491.
Defending champion Bradley McGee of Australia, who wore the yellow jersey for three days at the start of the recent Tour de France, was forced to pull out at the last moment due to health problems.
Later on Wednesday, Olga Slusareva of Russia won the second gold medal of the championships by claiming the women's points title for the third straight time.
Edita Kubelskiene of Lithuania came second with Yoanka Gonzalez of Cuba taking the bronze after the 22-lap 24km race.
And Franco Marvulli of Switzerland defended his men's scratch title.
The 24-year-old Swiss won the inaugural scratch world title - a 15km endurance race where riders can be eliminated if they are lapped - last year in Copenhagen.