Starting keeper Tim Weise and Philipp Bargfrede are fit, returning to training this week after minor injuries. Bremen are in sixth place on 40 points.
Former Germany international Hildebrand, who joined in October as a replacement for injured Ralf Faehrmann, will be out for an unspecified period of time. Schalke, in third place on 53 points, are in the running for a Champions League spot.
The Bundesliga season should end in a final four of the league's top teams with the champions then crowned in a final game to make it more exciting,
"My dream always is to have a real final stage with the top four teams fighting for the title; real highlights with semi-finals and a final.
"The football decision-makers should give up their conservative position and search for better solutions and then show the courage to change things," Holzhaeuser wrote.