Borussia Dortmund forward Marco Reus will not make his return in Saturday's Klassiker against Bayern Munich after sustaining a heel problem.
Reus, whose progress over recent seasons has been persistently hampered by fitness woes, has not featured for Thomas Tuchel's side since May's DFB-Pokal final defeat to Bayern due to an adductor injury.
The 27-year-old resumed training with Dortmund last month and was reported to be on the verge of a return to the matchday squad for German football's stand-out domestic fixture.
But Dortmund tweeted on Friday: "[Reus] has slight heel problems. To take no chances after his lengthy downtime, using him tomorrow is not possible."
Bayern boss Carlo Ancelotti expects Dortmund to cope without Reus, and suggested that the Germany international could become a wiser player as a result of his injury concerns.
"Reus is a fantastic player but I think Dortmund will be able to use others," Ancelotti said on Friday.
"Injuries are never easy for the players, but this is part of the game. I was injured myself for two years. Sometimes spells like these are helpful in learning for the future."