Three-time champion Mathieu van der Poel has pulled out of the 2022 cyclo-cross world championships in the US due to a back injury, the Dutch cyclist announced on Wednesday.
Separately, Belgium's Wout van Aert, who won the championships in 2016, 2017 and 2018, said he would also miss the event.
"Because of back pain I have not reached the desired levels since the Tour (de France)," Van der Poel said in a statement, issued by his Alpecin-Fenix team.
"I just want to get rid of it," added Van der Poel, who led the Tour de France for six days on his debut last year, before quitting ahead of the ninth stage to focus on the Tokyo Olympics.
"The only cure turns out to be a longer rest period and it would be stupid to interrupt this," Van der Poel said, adding it was a "disappointment" not to be able to defend his rainbow jersey in Fayetteville, Arkansas later this month.
The 26-year-old Dutchman said he was "not worried about the rest of my career, but I am frustrated not knowing how long this rest period will take."
Alpecin-Fenix have indicated that Van der Poel, who turns 27 on January 19, will only start his road season after putting the injury behind him and when he has been able to prepare properly.
"We want to optimise the healing process and that's not possible given the time constraints for a possible participation in the World Championships in Fayetteville," Alpecin-Fenix team managers Christoph and Philip Roodhooft said.
Van der Poel's Belgian rival, 27-year-old van Aert, said in a tweet from Team Jumbo-Visma that he would also miss the Arkansas event.
"It's a pity, but an inevitable function of the spring campaign," he said.