The League One champions have confirmed Leon Barnett, Ryan Jennings, Kevin McNaughton and Reece Wabara will be allowed to exit.
Midfielders Chris McCann and Jordan Flores are offered new deals.
Emyr Huws, Jack Hendry, Billy Mckay, Andrew Taylor, Dan Lavercombe and Danny Whitehead have all been out on loan but will return for pre-season.

The Australian impresario's death was confirmed on Facebook by Spencer Gibb, son of Bee Gees star Robin Gibb.
A cause of death was not immediately available.
Andrew Lloyd Webber was among those paying tribute, describing Stigwood as a "great showman" who "taught me much".
Spencer Gibb called him "a creative genius with a very quick and dry wit" adding that "Robert was the driving force behind The Bee Gees career".
Stigwood started out as an advertising agency copywriter in his native Australia before moving to the UK at the age of 21
There, he made his name representing English singer John Leyton, securing him a role on the TV show Harpers West One. The deal allowed Leyton to perform a song - Johnny Remember Me - which spent four weeks at number one in 1961.
By 1966, after a period of bankruptcy, he became a booking agent for The Who, luring them onto his own Reaction Records label, where they recorded the hit single Substitute.
He went on to manage Cream and Eric Clapton, before signing the Bee Gees in 1967 and steering them to international success with an intensive promotional campaign for the single New York Mining Disaster 1941.
By the early 1970s, though, the Bee Gees had fallen out of favour, and Clapton was inactive due to drug addiction. Stigwood turned his attention to musicals, producing the movie version of Jesus Christ Superstar and The Who's rock opera Tommy.
Having bought the management rights to Evita and Jesus Christ Superstar, Stigwood was instrumental in cracking down on unlicensed performances of the musicals in the US - including school productions - to ensure profits went into pockets of its creators.
He also formed RSO Records (short for Robert Stigwood Organization), where he resuscitated the careers of his two biggest acts - sending Clapton to the top of the charts with I Shot The Sheriff, and rebranding the Bee Gees as falsetto-voiced disco lynchpins on Jive Talking.
The Australian's midas touch continued in the late 1970s, when he produced Saturday Night Fever, making a global star of television actor John Travolta and selling 40 million copies of the Bee Gees-powered soundtrack.
Stigwood followed it with the evergreen teen musical Grease, and was particularly proud of casting fellow Australian Olivia Newton John in the role of Sandy.
But he faltered with the 1978 Beatles musical Sgt Pepper's Lonely Hearts Club Band - a fantastical but unfocused movie starring The Bee Gees, Peter Frampton and comedian Frankie Howerd.
"If you like the Beatles and you like movies, do yourself a favour and stay away," wrote influential US film critic Jonathan Rosenbaum. Audiences took note, and the film flopped at the box office, although the soundtrack sold well.
Stigwood went on to produce the similarly-disappointing sequels Grease 2 and Staying Alive - but found success later in life with the Madonna-starring musical Evita, which won the 1997 Golden Globe for best film.
The movie's lyricist, Sir Tim Rice, paid tribute to Stigwood on Twitter, calling him "extraordinary, innovative [and] generous".
"[He was] a vital part of my life," he added.
Wigan Athletic have announced that four players will leave the club when their contracts expire during the summer.
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Robert Stigwood, who managed Cream and the Bee Gees before producing the rock musicals Saturday Night Fever and Grease has died at the age of 81.