"We actually alternated the two quarterbacks," interim head coach Wade Phillips said of Keenum and
Schaub started under center on Sunday against the Broncos.
"I think Thursday when we start throwing the ball around, and certainly see how Case is on Friday after throwing the ball, we'll get a better idea," Phillips said.
Keenum has thrown for nine touchdowns and six interceptions in 2013, and has a quarterback rating of 78.2.
Phillips also said that Yates is not an option to start "right now", because Keenum and Schaub have both taken the lion's share of snaps in 2013.
"Both the guys have played a whole lot," Phillips said. "Going into the last game, they give us the best opportunity."