Foster, who leads the NFL in rushing with 920 yards, said via Twitter that he was flying to Los Angeles to be with family members. A team spokesman told the newspaper the absence was excused, and Foster is listed as probable on the Texans' injury report.
"Zac is still not feeling better, but hopefully he'll be released (from the hospital) this afternoon," Kubiak said at his Friday news conference. "My expectations are he'll be ready to go (Sunday).
"He just hadn't been feeling well, just trying to get fluids in him and get him feeling better. I thought maybe he'd be over here today, but (he) didn't feel good about that this morning."
Diles, fellow linebacker Xavier Adibi and Schaub are listed as questionable on the injury report. Schaub, who required treatment for bursitis in his right knee, fully participated in practice and will start Sunday, said Kubiak, who added that Adibi also will play.
"(Schaub) did everything that he does on Friday," Kubiak said. "He's fine, and everything responded good yesterday."
"(Owen Daniels) did field work this week, so that's a positive, but he's still got a ways to go," Kubiak said. "He's not going to be ready to go this week, and we'll see where he's at next week."