Gillespie, 34 was released by United this January and has been snapped up by Stuart McCall after the Northern Ireland international had an unsuccessful trial at Leeds United.
He was signed by Neil Warnock in August 2005 after a successful trial; making his debut in a 4-1 win over Leicester City - whom had released him only a few months previous. Gillespie made a total of 62 (+41) appearances for the Blades and scored four goals.
He is likely to feature in the Bantams reserve fixture against Barnsley Reserves tonight. Blades-Mad would like to wish Keith the very best for the future.