Ewan had aimed to win stages at all three Grand Tours this season but, after picking up two stages at the Giro d'Italia, he crashed out of the Tour de France with a broken collarbone in the first sprint.
The Australian has since returned to training but has not been deemed ready for the Vuelta, which begins in Burgos on Saturday.
"We needed to adjust our Vuelta line-up, which is now more focused towards the hilly and mountain stages," said direcetur sportif Nikolas Maes.
One of Ewan's lead-out men, Jasper De Buyst, had himself been ruled out after a collision with a car while training a fortnight ago, and other components of the sprint train such as Roger Kluge and Tosh Van Der Sande are also sitting out the Vuelta. Kluge recently raced on the track for Germany at the Tokyo Olympics.
Lotto Soudal have instead selected a youthful eight-man team that boasts an average age of just 24.
Florian Vermeersch, a Classics prospect with a fast finish, will fill in for Ewan and try his hand in the sprints, leaning on Frederik Frison for support. He is one of four Grand Tour debutants in the squad, alongside Sylvain Moniquet, Maxim Van Gils, and Andreas Kron, who has enjoyed a brilliant first WorldTour season, with stage wins at the Volta a Catalunya and Tour de Suisse.
Harm Vanhoucke will be aiming for increased consistency and a possible general classification effort after impressing at the past two editions of the Giro d'Italia, while the eight-man squad is rounded out by Steff Cras and Britain's Matthew Holmes.
"Guys like Andreas Kron and Harm Vanhoucke have already proven that they can obtain some nice results. They will be supported by Steff Cras, Matthew Holmes, Sylvain Moniquet and Maxim Van Gils. With Frederik Frison and Florian Vermeersch, we have two powerhouses in our team," said Maes.
"Overall, our selection doesn’t have a ton of Grand Tour experience yet, but they all have big potential. I am convinced that each one of them will prove himself at La Vuelta. With these young guys, we certainly can’t expect them to be there every day, but our ambition is to win a stage, which is in my opinion more than justified with this team.
"We will mainly be aiming at the transition stages and the tough uphill finishes. On paper, there are some really nice opportunities to show ourselves."
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