Marco Reus and Mats Hummels are still yet to return to training for Borussia Dortmund.
Club captain Reus sat out of Wednesday's 2-1 DFB-Pokal win over Borussia Monchengladbach with a muscular injury.
The Germany forward had only returned from a bout of illness ahead of last weekend's 0-0 Revierderby draw at Schalke and centre-back Hummels is now laid low with a sickness bug of his own.
Goalkeeper Roman Burki, who has also been ill, is back working with his team-mates ahead of Saturday's Bundesliga game against Wolfsburg at Signal Iduna Park.
"Roman Burki trained and is feeling good. Marco Reus and Mats Hummels did not. We still have to wait on their progress," head coach Lucien Favre said.
Julian Brandt could be called upon to start if Reus remains sidelined and Favre praised the former Bayer Leverkusen star, who scored for the first time since the opening weekend of the Bundesliga season with a brace to down Gladbach.
"Julian Brandt stood tall and played a great game from [attacking] midfield," he said. "Not only did he score two goals, he also effectively helped out in defence."
Dortmund lie fifth in the Bundesliga, a point and a place behind Wolfsburg after nine matches.
