It will mark the first regular-season NFL action for Keenum, 25, who signed with the Texans after going undrafted in 2012.
"He's given me confidence through camp," Kubiak said of Keenum. "He continues to grow. We're looking for a spark and he deserves an opportunity.
"We just want him to go out there and react. That's why he's on this football team."
Schaub was injured in the third quarter of last week's game against St. Louis. He hurt his right ankle. T.J. Yates took over in that game at quarterback but had two interceptions, one of which was returned 98 yards for a touchdown.
Schaub set an NFL record for having interceptions returned for touchdowns in four consecutive games this year.
Houston (2-4) takes on the 6-0 Chiefs in Kansas City Sunday.