MIAMI -- Zach Thomas had the idea Wednesday, thinking maybe he could sign a one-day contract with the Dolphins and retire as part of the franchise.

His agent asked the team. Thomas received his answer within minutes.

So on Thursday, Thomas signed a one-day contract, officially worth $1 -- but in actuality, worth so much more to the linebacker, who long lamented not having the chance to properly say farewell when the Dolphins released him two years ago.

With that, Thomas finally said good-bye.

"I'm a little bit nervous right now," he said at the Dolphins' training facility in Davie, Fla. "More nervous than any game I ever played."

Just a fifth-round draft pick out of Texas Tech in 1996, Thomas became a star during 12 seasons with the Dolphins. He was one of the faces of the franchise along with the likes of Dan Marino and Jason Taylor, who became Thomas' brother-in-law.

Thomas played in 168 games for the Dolphins, recording 19.5 sacks and 17 interceptions, and he was chosen for seven Pro Bowls.

"As the team's owner, I want to welcome him back to the Dolphins, and I certainly hope he continues to make his presence felt," Stephen Ross said. "He's a great role model for our players, and we're proud of everything he has done throughout his career to represent this franchise. He gave his heart and soul to this team, and we all were better for it."

Thomas spent the 2008 season with the Dallas Cowboys, then was in camp last year with the Kansas City Chiefs, who released him before the season after unspecified injury issues. He didn't play again.

"The game has been good to me," said Thomas, who was joined by several friends and family; agents Drew and Jason Rosenhaus; his wife, Maritza; and their 4½-month-old son.

Like his final season, Thomas' stay with the Dolphins also ended after an injury. One of the NFL's most durable players for more than a decade, Thomas appeared in just five games for Miami in 2007 after his car was rear-ended, creating a whiplash injury that caused him to suffer migraines for weeks.

Thomas also dealt with numerous concussions in his career, and he pledged earlier this year that, upon his death, he'll donate his brain to the Center for the Study of Traumatic Encephalopathy at Boston University School of Medicine. Thomas has often said he doesn't know how many concussions he had in his career.

On Thursday, Thomas said he felt fine.

"I think it's great that Zach is retiring as a Miami Dolphin," Marino said in a statement. "As someone who spent my entire career with the Dolphins, I can appreciate what it means to Zach to finish his career as part of the team that meant so much to him during his playing days."

Copyright 2010 by The Associated Press