Barker, who skipper Posh under 23s last season, has been linked with a move to Crewe Alexandra or Crawley Town.
Barker, 21, emerged from the club’s Academy, but started just four EFL Trophy games for Posh. He also made one substitute appearance in the EFL, the FA Cup (against Premier League side Burnley), the League Cup and the Trophy.
Barker spent time on loan at non-league clubs King’s Lynn and Wrexham while on the Posh books.
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