Nathan Thompson has sealed a move to Peterborough.
The right-back has signed a two-year deal with Pompey’s League One rivals.
Thompson will make London Road his next destination after failing to agree a new deal with the Blues this summer.
Posh boss Darren Ferguson admitted he was shocked he was able to sign Thompson.
He told www.theposh.com said: He is a very good right back, he is athletic and aggressive. I will be honest and say that I am very surprised we have been able to get him.
‘When he left Portsmouth, he was going to the Championship, but for whatever reason it didn’t come through.
‘I didn’t think I would be able to get a right-back of this magnitude if I am honest, but when it became a possibility, we have acted quickly on it because if Jason (Naismith) is going to move on for regular football, then I have to have two right-backs.’