Hixon was officially placed on injured reserve because of a torn ACL, ending his season. He was hurt during Monday's win against St. Louis, suffering his second torn right ACL in as many years.
Clayton appeared in six games for the Giants last season after being signed in late November, then was among the final roster cuts earlier this month. He caught two passes for 45 yards in four games this preseason.
In his brief stint with the Giants last year, Clayton had two receptions for 19 yards. The former first-round draft pick played in the United Football League last season before joining the Giants.
Clayton spent his first six NFL seasons with Tampa Bay, which made him the 15th overall pick of the 2004 draft. He was cut by the Bucs in September 2010.
In 90 career NFL games, including 56 starts, the LSU product has 223 catches for 2,955 yards and 10 touchdowns. He had a fantastic rookie year, catching 80 passes for 1,193 yards and seven touchdowns, but never came close to matching those numbers over the next five seasons.
Clayton may see action immediately this Sunday against Philadelphia, as Giants receiver Mario Manningham is considered doubtful because of a concussion.