According to the Armando Salguero (@ArmandoSalguero) from the Miami Herald,
“The Dolphins are comfortable -- for now -- with the work rookie Jamil Douglas and third-year player Dallas Thomas have done in camp, they're not likely to move significantly right away. It would require one or both those players fading in camp or performing poorly in the preseason for the Dolphins to rethink their stance.”
According to Salguero the Dolphins and Mathis’ agent Drew Rosenhaus have talked “parameters” of a deal but the two parties are about 2-3 million apart in terms of compensation. The Dolphins would like to do “adeal that doesn't tie them up for a second season although it might be a two-year deal.