Poels claimed Sky's first-ever Monument victory at Liège-Bastogne-Liège in 2016, but a nagging knee injury will force him to miss the three Ardennes Classics: the Amstel Gold Race, La Flèche Wallone and Liège.
Knee pain has sidelined the 29-year-old Dutchman since the end of February, scuttling his plan to race Paris-Nice after a nice run of early results.
"It's been a tough time because I've been on the bike, off the bike, on the bike," Poels said via the release.
"Everybody knows you need to have done a certain amount of work to be super good in the Ardennes Classics. If you've not put the hours in and done the long days – Liège-Bastogne-Liège is more than 250km – then you won't do well."
For Poels, the break from racing has been particularly frustrating after a strong start that saw him among the top five overall at the Volta a Valencia and the Ruta del Sol.
"It's always disappointing when you can’t race or train," he said.
Get The Leadout Newsletter
The latest race content, interviews, features, reviews and expert buying guides, direct to your inbox!
"Last week was the first time I’d had a better week of training - the first time I’d got consistent hours in."
The timeline for Poels' return is unclear, though he is targeting the Tour de Romandie in the run-up to the Tour de France. The initial plan was for Poels to race both the Tour de France and the Vuelta a España this season, though whether that is still a possibility given his derailed spring preparation remains an unknown.
"I did a nice ride today and the feeling was OK, so hopefully if this week carries on like this then I might go to Romandie to get some competitive action and support the team. To be back racing would be amazing," he said.
"Then I should head to an altitude camp as preparation for the Tour de France. I think the team wants me for the Tour so I’ll work hard for that and go there to support Chris [Froome]."
Sky has other options for the Ardennes even without Poels making the start. Michal Kwiatkowski, fresh off his first Monument victory at Milan-San Remo last month, won the Amstel Gold Race in 2015 and has finished on the podium at Liège.
Poels is not the only would-be contender sidelined by injury for the Ardennes this year. Quick-Step Floors announced Tuesday that Julian Alaphilippe, who has finished on the podium of all three races, will miss the trio of hilly one-day races with a knee injury of his own.
