The 25-year-old holds on to the job despite Matt Schaub returning to practice following a foot and ankle injury, which forced him to miss the team's defeat to the Kansas City Chiefs earlier this month.
Head coach Gary Kubiak told reporters: "Case will start this week. Actually, I talked to Case and Matt, I think, Tuesday before I gave them their break and talked to the team this morning. But Case will start and hopefully we'll grow from last week. I thought he did some really good things.
"I thought we played some clean football and we're going to have to do that here down the road to improve. That's the way we started working today. Matt's fine and it's just the decision I made based on what I saw take place last week with Case and him taking advantage of an opportunity.
"I want to see him move forward. He's got to improve. He's definitely got to go and improve. With this football team we're playing, our football team's got to improve around him. Like I said, a decision for this week."