Sagnol, who started his playing career at St Etienne in 1995, also played for Monaco and Bayern from 2000-08, becoming France Under-21 coach last year.
He won 58 international caps and helped France reach the World Cup final in 2006.
The 37-year-old Sagnol's position at Bordeaux is expected to be officially confirmed later on Friday, the source said.
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- Bayern Munich
- Francis Gillot