German Jan Ullrich has been forced to delay his preparations for this year's Tour de France because of an injury.
Ullrich won the Tour de France in 1997 as a 23-year-old
Ullrich, who won the Tour in 1997, has pulled out of the Circuit de la Sarthe on 4-7 April following the recurrence of an old knee injury.
Ullrich has irritated an injury he first sustained in March, according to his T-Mobile team's doctor.
Ullrich said: "When the knee is better I will start to prepare for the Tour with my usual discipline."
Ullrich had already decided not to race in cycling's spring one-day classics to ensure he was in the best shape possible to try to recapture his Tour de France crown.
Ullrich, 32, has been backed to win this year's Tour de France by American cycling legend Lance Armstrong.
Ullrich has finished runner-up in the Tour de France five times, three times behind Armstrong, who was champion for seven successive years before announcing his retirement after his 2005 success.
Ullrich said: "I was really looking forward to competitive racing. From now on I will pay more attention to ensure the irritation is fully healed, then I can progressively increase the training load."
All Ullrich's major rivals have already shown their early season form this month.
Italian Ivan Basso won the challenging three-stage Criterium International; Kazakhstan's Alexandre Vinokourov triumped in the Tour of Castilla and Leon; and American Floyd Landis came out on top in the week-long Paris-Nice.