The Texans never have had a winning record, and Carr often was the scapegoat. He completed 60 percent of his passes, but also threw 65 interceptions and was sacked 249 times in five seasons.

Houston hoped Carr would flourish under new coach Gary Kubiak last season, but the Texans went 6-10.

Williams, formerly Domanick Davis, is Houston's career rushing leader with 3,195 yards. He spent all of last season on injured reserve with a knee injury.

Also Friday, the Texans re-signed former Heisman Trophy winner Ron Dayne, who joined the Texans just before last season and blossomed late in the year, rushing for 429 yards and five touchdowns in December.

The Texans released Carr a day after signing Matt Schaub and saying he would be their starting quarterback. General manager Rick Smith said Thursday the team was trying to trade Carr, who had two years left on a contract that was to pay him $11.5 million for those seasons.

A message left for Carr's agent, Mike Sullivan, was not immediately returned Friday. The team said it would have no immediate comment.

Williams sat out most of training camp last season with soreness in his right knee. He showed up in the Texans locker room on Jan. 1, saying he had legally changed his last name from Davis to Williams, his mother's maiden name.

He missed five games in 2005 before undergoing arthroscopic knee surgery. He returned for training camp and declared himself healthy, but soon stopped practicing because of a bone bruise in the knee.

The Texans signed Dayne two days after placing Williams on injured reserve in September. Dayne, the 1999 Heisman Trophy winner, had been released by Denver, where Kubiak was formerly the offensive coordinator.