Reports surfaced earlier this week claiming that the summer signing from Borussia Monchengladbach was struggling for fitness ahead of the new campaign.
That has now been confirmed by the Catalan outfit, although the injury is not believed to be serious.
"New first team goalkeeper Marc-Andre ter Stegen suffered a blow to his spine during the second of Monday's two training sessions," a club statement read.
"Tests early on Tuesday confirmed the injury of the German goalkeeper who will work on his own for the next training sessions."
As a result, Claudio Bravo, who also arrived this summer, is expected to be between the sticks for the league opener against Elche on August 24.