The Derby-born player started his career at Celtic after being bought out of the army, before moving to Stoke City in 1994.
He spent four years with the Potters before a £50,000 transfer to Warren Joyce's Hull City in November 1998. He was instrumental in the Tigers' successful relegation battle and has been a mainstay at the back ever since. He was also team captain for most of that time before handing over the armband to Ian Ashbee last year and taking on the roll of 'club captain' instead.
That signalled the end of his regular participation in the first team, with Peter Taylor preferring his own signings Damien Delaney and Marc Joseph to provide the backbone of City's promotion-winning team.
He made 219 first team appearances in all competitions, although only two of them were since last November, and the lack of first team opportunities is sure to be the reason for his move. He scored three times in a Tigers shirt.
He was also the longest-serving player for City. That title now belongs to 21-year-old Nathan Peat, who came through the youth ranks and signed pro terms in April 2002. Having been an unused sub back in 1999, it wasn't until September 2002 that he made his first team debut. The only current players who turned out before then were Jan Molby signings Ian Ashbee, Stuart Elliott and Stuart Green, all making their debuts a month earlier.
City have already brought in Southend defender Leon Cort this summer and Junior Lewis is also expected to sign so Taylor is unlikely to seek further cover for Joseph and Delaney following Whittle's departure.