Mattis made 82 appearances for the Saddlers, scoring six goals
Experienced midfielder Dwayne Mattis is one of seven out-of-contract players being released by Walsall.
Home-grown youngsters Mark Bradley, Netan Sansara, Sam Adkins and Richard Davies are also leaving the Saddlers, as well as Peter Till and Josh O'Keefe.
But 22-year old centre-back Manny Smith has agreed a new two-year deal to stay at the Banks's Stadium.
Julian Gray, Jamie Vincent, Alex Nicholls and Richard Taundry have all been offered new deals.
There are also new contracts on the table for Mark Hughes, Rene Gilmartin, Darryl Westlake and Will Grigg.
The aim now is to continue to push on and help take the club forward
Manny Smith on his new two-year deal
"At this time of the year some difficult decisions have to be made but we would like to thank every player for their hard work and effort during their time at Walsall Football Club," said Saddlers boss Chris Hutchings.
Smith's new contract should end speculation that the former Solihull College student would move on this summer after attracting interest from Championship sides.
"I'm really pleased to have signed a new contract," he said.
"I'm committed to this football club and am just pleased to have my future sorted out.
"The aim now is to continue to push on and help take the club forward."
Chris Hutchings had only five senior players with contracts that already stretched into next season - Darren Byfield, Matt Richards, Clayton McDonald, top-scorer Troy Deeney and Steve Jones.
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