Road World Championships
Date: 23-28 September Coverage: Live on BBC Red Button and BBC Sport website; highlights on BBC2
Kirchen led the Tour de France for four stages in July
Luxembourg's Kim Kirchen has joined World and Olympic time trial champion Fabian Cancellara in pulling out of the 2008 Road World Championships in Italy.
Kirchen would have been a medal contender in the blue riband event of the men's road race to be held Sunday, but said he was in no form to compete.
"I don't think I have sufficient form to get a good result, so I prefer not to race at all," he said.
Cancellara pulled out this week citing a lack of motivation ahead of the race.
"After my success in Beijing, I've not been able to find enough energy to keep myself motivated," said the Swiss rider.
"I don't have enough energy to take part and try to defend my title."
Cancellara, 27, won time trial gold at the last two World Championships and at the Beijing Olympics. He also took road race bronze in China.
Earlier this month, Britain's Mark Cavendish - currently regarded as cycling's top sprinter - also pulled out of the World Road Race Championships citing fatigue.
Team Columbia rider Kirchen, who wore the yellow jersey at this year's Tour de France, will be replaced by Claude Wolter in a team that will be led by the Schleck brothers, Andy and Frank.
It is the first time ever that Luxembourg will have the luxury of using a nine-man team.