Fritz recently signed a three-year contract extension with the Bundesliga side. The deal keeps him at the club until 2012.
Fritz has struggled with injuries in recent months.
“I’m on the right road. We are increasing the workload daily to see how the muscles react,” said Fritz.
“I need a few more days but hope to be able to train with the rest of the team by the end of the week. Problems with muscles are always very sensitive issues.”