The 10th overall pick of the 2006 NFL draft and 2004 Heisman Trophy winner at the University of Southern California, Leinart likely will back up fellow USC alum Carson Palmer.
He went 10-of-13 through the air for 57 yards and a touchdown in two games for Houston last season.
Over his five-year career with Arizona and Houston, Leinart has completed 350-of-608 passes for 3,950 yards with 15 TDs with 20 interceptions.
ESPN reported Leinart would be penciled into the No. 2 slot ahead of Terrell Pryor with the Raiders.