German rider Jan Ullrich has pulled out of Wednesday's time-trial at the World Championships due to a stomach problem.
Ullrich has had a year to forget
T-Mobile rider Ullrich - 1997 Tour de France winner and 1999 world time-trial champion - will be replaced in Verona by Uwe Peschel.
It is unclear whether he will ride in Sunday's road race.
Ullrich, 30, disappointed at the Athens Olympics finishing 19th in the road race after starting as one of the pre-event favourites.
The 2000 Olympic champion said he was left with no option but to withdraw.
"At the moment I just can't sit on the saddle," Ullrich told his website.
"It's impossible for me to get in a condition that would allow me to be in contention for the title in just two days.
"Whether I can compete in the road race will be decided later this week.
"I can't eat anything without being sick. I don't know whether it's food poisoning or a virus."