The Texans acquired quarterback Ryan Mallett in a trade with New England and released Case Keenum, who had been competing with rookie fourth-round pick Tom Savage for the No. 2 role behind Ryan Fitzpatrick.
The 6-foot-6 Mallett, a third-round pick in 2011, was Tom Brady's backup the past three seasons, but was passed up in training camp this year by second-round draft pick Jimmy Garoppolo. Mallett played in only four games in three seasons in New England and he'll have a bigger opportunity in Houston under Bill O'Brien, who was the Patriots' offensive coordinator in Mallett's first year.
Keenum, a record-setting quarterback at the University of Houston, went 28 for 52 with two interceptions in the preseason, not enough to keep his roster spot after he started eight games last season.
The Texans also claimed receiver Damaris Johnson from the Eagles, cornerback Daryl Morris from the 49ers and offensive tackle Jeff Adams from Tennessee. Johnson was a record-setting kick returner at Tulsa before the Eagles signed him as an undrafted free agent in 2012. Johnson had 21 catches for 270 yards in two seasons with Philadelphia.
Receiver Mike Thomas and safety Chris Clemons were cut. Thomas was expected to challenge DeVier Posey for the No. 3 receiver position. Thomas was a fourth-round draft pick in 2009 by Jacksonville and hasn't played since finishing the 2012 season with Detroit. He has 176 catches for 1,796 yards in his career.
Clemons played five seasons in Miami and was brought in to provide veteran leadership after Manning signed with Cincinnati. The Bengals left Manning off their 53-man roster and the Texans decided to bring him back and let Clemons go.
Manning was a second-round pick by Chicago in 2006 and played his first five seasons with the Bears. He was signed along with cornerback Johnathan Joseph in 2011 to provide leadership to a secondary that was part of the league's worst pass defense the previous season. Manning made 124 tackles and intercepted four passes in his previous three seasons in Houston.
He started six games last year before his season ended with a right knee injury in a mid-October game against St. Louis. Manning's agent, Russel Hicks, confirmed on Sunday that Manning will sign with the Texans pending a physical.
The Texans also announced their practice squad: receivers Travis Labhart and EZ Nwachukwu, defensive end Keith Browner, linebacker Max Bullough, tight end Anthony Denham, fullback Toben Opurum, cornerback Marcus Williams and offensive linemen Matt Feiler, James Ferentz and Alex Kupper.