Texans backup battle goes down to last preseason game, and possibly beyond

In Houston, coach Gary Kubiak knows his starting quarterback will be Matt Schaub.  But Kubiak still doesn’t know who’ll be Schaub’s primary understudy. The battle between T.J. Yates and Case Keenum continues into the preseason finale, where Keenum will get the start and the two candidates for No. 2 will each play one half of…