Gueret, who has been the club's second choice keeper for the past four years, has now returned to France in the hope of securing a a contract with a new team.
"Dennis has told me I am not part of his plans," said Gueret.
"I am not sure what I will do now but I am looking for a club in France. But I am not sad to be going because of the way things happened to me."
Although his first team appearances were limited, Gueret kept 10 clean sheets in his twenty games for the club and set a record of four in a row in 2001. He made four appearances this season after Tony Warner was injured but made way for Andy Marshall after Wise appeared to lose faith in him.
Marshall meanwhile is close to securing a new contract with The Lions. The former England under-21 goalie has had talks with the club and is expect to meet with Millwall chairman Theo Paphitis early next week.