The winger recently underwent a minor operation that ruled him out of England's final two World Cup qualifiers, but manager Arsene Wenger has revealed that the problem flared up again in training.
"He had a setback. He had to stop, to jog again, I don't think we will see him against Dortmund, nor Crystal Palace nor Chelsea," he said.
"He is at least two weeks away now."
Arsenal have continued their blistering start to the season in Walcott's absence, while Tottenham's Andros Townsend impressed on the right flank as England booked their place at next summer's World Cup.