Dolphins cut defensive anchor Thomas after 12 seasons in Miami

"In addition to his numerous accomplishments on the field, he was a leader off of it as well," Ireland said. "We want to thank Zach for everything he has done for the Dolphins organization and the South Florida community."

He was remarkably durable in his first 11 seasons, missing only 13 games, and recorded a career-best 165 tackles in 2006 -- an indication he wasn't exactly slowing down.

But Thomas missed two games in September this season because of a concussion, and on Oct. 21, he took another hard shot off the field. Thomas had eight tackles in Miami's 49-28 loss to the New England Patriots, and as he and his wife drove home that day, their vehicle was rear-ended on Florida's Turnpike.

Originally, the Dolphins said Thomas was uninjured in that crash. But he experienced numerous migraines following that wreck, and never got back on the field in 2007.

He was inactive for the next seven games before the Dolphins put him on injured reserve, officially ending his season and sparking widespread speculation that his time with Miami could be drawing to a close.

A week ago, new Dolphins coach Tony Sparano said no decisions had been made about Thomas' status for 2008.

"We're doing what we have to do," Sparano said on Feb. 7 when asked about Thomas' future.