Hard-hitting LB Thomas to re-join Dolphins, announce retirement

Free-agent linebacker Zach Thomas is expected to sign with the Miami Dolphins, with whom he played 12 seasons, and then announce his retirement Thursday at a 4 p.m. ET news conference.

Thomas' career in Miami ended in 2007, and he signed with the Dallas Cowboys as a free agent in 2008, playing one season there. He was released by the Kansas City Chiefs after the 2009 preseason.

Thomas was a fifth-round draft pick of the Dolphins in 1996, and his emergence prompted him to replace current Jacksonville Jaguars coach Jack Del Rio at middle linebacker. Del Rio, who was cut during the preseason, went on to retire.

The undersized, hard-hitting Thomas was the anchor of the Dolphins' defense for 12 seasons and was among the most productive linebackers in the NFL for years before a series of concussions sidetracked his career. He's a five-time first-team All-Pro and seven-time Pro Bowl selection.