Saints have confirmed that eight out-of-contract players will be released this summer - including Tommy Forecast.
Forecast is coming to the end of a lucrative five-year deal that did not include a single first-team appearance foillowing his arrival from Spurs in the summer of 2008.
Full-backs Richardson and Butterfield, who spent the last six weeks of the season on loan at Bolton, made 64 and 53 league and cup appearances respectively after arriving from Charlton four years ago.
Seaborne's time at Saints was marred by the nightclub attack that left him with serious head injuries midway through his three-and-a-half years with the club.
He made 53 appearances for Saints but only two of them came after sustaining life-threatening injuries in September 2011.
The 26-year-old spent three months of the 2012/13 season on loan at Charlton (one month) and Cherries (two months).
Left-back Ryan Dickson made 23 appearances during his three-year spell at St Mary's
Two academy products are on their way.
Reeves, 21, a left-sided utility player from Verwood, leaves after maing 13 appearances fore the first team -including three in the Premier League (as a substitute).
Hoskins, 20, has spent three months on loan at Stevenage since Christmas, having made two of his three League Cup appearances for the club at the beginning of the season.
Seidi, a 20 year-old forward from Guinea Bissau, did not make a first-team appearance during his season with the club