The 34-year-old defender made 31 appearances for the Clarets in 2007-8 following his arrival on a free transfer from Wigan Athletic.
Unsworth's one-year deal expired in the summer of 2008 but Owen Coyle was willing to offer him a dual player and coaching role.
The former Everton and England defender however expressed a desire to extend his playing career and became a free agent from July 1 2008
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