Klint Kubiak said the Raiders need "another week" before naming a Week 1 starter after Fernando Mendoza's extended preseason audition ended with an 8-of-15, 86-yard first half.
Mendoza's biggest mistake came on an interception returned 80 yards for a touchdown, and Las Vegas went into halftime trailing Houston 20-3 without an offensive touchdown.
Kirk Cousins did not play Thursday, a usage pattern that reinforced expectations the veteran could still open the season while the No. 1 overall pick develops.
Las Vegas has one preseason game left, but Kubiak has already signaled he prefers not to rush the 22-year-old Mendoza into the starting role.