Sources told ESPN NFL Insider Adam Schefter that Osweiler is not even expected to play in Saturday's game against the Tampa Bay Buccaneers.
Jackson said he informed the team Wednesday of his decision to start Kizer against the Bucs.
"[Kizer] has made a lot of progress by investing the time necessary to learn our offense, working hard to improve on his fundamentals while also effectively moving the offense in preseason games," Jackson said in a statement released by the team. "Development is so important for a young quarterback, this is the next step he needs to take and he deserves this opportunity.
"We are very excited about seeing DeShone in the role of starter for this week, as he is certainly positioning himself well to earn the starting job heading into the regular season."
It appears that Kizer is going to win the starting job heading into Week 1 provided that he doesn't fall on his face in the third preseason game. He could work his way into the QB2/streaming conversation.