Christian picked up an ankle injury playing for Germany against the USA on Wednesday, a match in which he captained his country and smashed a free-kick past Kasey Keller.
Meanwhile, Glenn has to decide whether to add Stephen Clemence and Gary Doherty to the squad. Both came through another reserve outing against Watford on Tuesday.
"It's a bit unfortunate after international week, we might have lost Christian Ziege," reported Glenn. "We don't know yet, he's got to have some scans done.
"He played extremely well for Germany.
"There is no-one else, Deano is there or there abouts - I can't see him being 100 per cent fit for Saturday.
"Obviously we're a little bit strapped in this area, we've got 16 fit players to train and hopefully the international lads will come back fit."
Christian Ziege and Dean Richards are doubts for the trip to Middlesbrough on Saturday.