Running back Arian Foster missed Wednesday's practice because of a back injury.
The fifth-year veteran left Sunday's loss to the Colts in the first quarter because of the back injury. It was the second consecutive game in which exited early, as he left the Week 7 loss at Kansas City because of a hamstring injury.
On the game's first play against the Colts, Foster was targeted for a pass over the middle, but it went for an incompletion. After that opening drive, Foster went to the locker room and emerged later in a sweatshirt.
"He's with the doctors and that's being diagnosed," acting head coach Wade Phillips said on Wednesday.
When asked about the likelihood of Foster taking the field at Arizona, offensive coordinator Rick Dennison was uncertain.
"I have absolutely no idea," Dennison said. "We'll come up with some running backs. We'll have a set. We'll do all we can. We have a good line and a good system I believe and we'll make our yards."
The Texans will practice again on Thursday at the Houston Methodist Training Center.