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.
"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.