Walker joined the Vale back in May 2006 but has only made 17 apperances for the Burslem Club.
27-year-old Walker also had a loan spell at Wrexham last season made his last apperance for the Vale back in January 2007. Since then the Stafford born defender has had a torrid time with tendonitis in his knee.
Walker will now train with the Vale until he can fix himself up with a new club.
