Gregor Robertson has become the latest player to have his Cobblers contract terminated.
The 31-year-old, who can play at left-back or as a central defender, was brought in by manager Chris Wilder during last season’s January transfer window and made 39 appearances for the club.
“As with Emile Sinclair, Gregor was a player we needed at that stage of our development and he came in and did a good job,” said Wilder.
“We are now looking to move on and it is in Gregor’s best interests to move on and play regular football.
“We are aware the recent exits have left us a little short on numbers but we do have a couple of additions in the pipeline to boost us.
“Gregor is an excellent professional and he leaves with our thanks and best wishes.
“It is another tough decision but a decision made to help take us forward.”
Robertson’s most recent first-team appearance came in the 2-1 defeat at Tranmere Rovers on December 28, in which he was withdrawn after 31 minutes with a rib injury.