Germany international Arne Friedrich has confirmed he is injured and unable to feature in pre-season with Wolfsburg.
Due to a surgery on his spine, the 32-year-old missed four months of last season and he has suffered a complication which has caused a setback.
Friedrich has been ruled out for six weeks and has travelled to Berlin to undergo a rehabilitation programme in a bid to be fit for the new Bundesliga season.
The defender said on his personal website: "Last season I was seriously injured after surgery on my intervertebral discs and now I am certified unfit for football due to complications.
"The issues are more serious than we first thought. I have been certified unfit for a duration of six weeks overall."