The 32-year old defender has signed a 'permanent contract' with the Latics and will be unveiled to the press on Wednesday morning.
"After a meeting with him on Monday and discussions all day Tuesday, Gary was the only candidate we considered, because we are so convinced of his qualities," said Wigan chairman David Sharpe told the club's official website.
"He knows who we are as a football club and shares the same football philosophy. He is a natural leader who commands respect from everyone around him.
"People will talk about his lack of experience, but every young coach is in the same place, and there are many examples of young coaches being given opportunities and being successful.
"For me, the timing was important. We will look to get a reaction in the next five games and this period crucially gives Gary a chance to look at the players until the end of the season. Plus, it enables us to start working now with a manager we know will be in place next season.
"Everyone associated with Wigan Athletic is feeling pain at the moment, but we have now taken measures to address the situation and the most important thing is that we have a definite blueprint for the future."
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