"Everything should be OK," Kubiak said. "I expect him here tomorrow. If that's the case, and he's doing what he normally does, he'll be out there."
Schaub's agent, Joby Branion, would not comment on the quarterback's status.
Kubiak said he did not know how Schaub hurt his knee. He met with Schaub on Tuesday morning and said Schaub seemed fine.
"I actually met with Matt yesterday morning for about an hour in the morning, just talking about things, and he was doing fine," Kubiak said Wednesday, according to the team's official website. "He went home with his wife and had some problems and called us, we sent him to the doctor, and then that's where it went from there."
Schaub called the team later in the day to say that his knee was bothering him. He was hospitalized overnight, and Kubiak says the team wanted to keep him there Wednesday as a precaution.
"Just needed some rest, needed some treatment," Kubiak said. "We made a decision that it was best to get it there than sit around here all day."
Schaub ranks fifth in the AFC in completion percentage (64.2) and yards passing (2,320). Dan Orlovsky is Schaub's backup, and Matt Leinart is next on the depth chart.
Schaub started every game last season and the first nine this year. He missed five games in 2007 with a shoulder injury and five more in 2008 with a strained ligament in his left knee.
"My preparation won't be any different," Orlovsky said. "Who knows what's going to happen with Matt (Schaub)? I'll prepare the way I need to and just go and run the offense. I'm not going to try to be Superman. I'll just try to go and run the offense and let those guys on the outside make the plays, put our team in good situations and give us a chance to win."
Star receiver Andre Johnson first heard about Schaub's injury Wednesday morning. He planned to call Schaub later in the day.
"I'm definitely concerned," Johnson said. "I was surprised to hear about it. I noticed he wasn't there in the meeting."
Orlovsky guided the first-team offense in practice for the first time Wednesday.
"I understand the responsibility -- I'm excited about it, if it comes to that," Orlovsky said. "It's only Wednesday. The guys in this locker room know that I prepare like I have to take the first snap on Sunday morning. That's not going to change. If needed, I'll be ready to go."
The Associated Press contributed to this report.