Brodie Croyle is expected to start in his place.
Cassel sprained his left knee in Kansas City's third preseason game Aug. 29. He returned to practice Monday. Though he's getting better every day, Cassel's been limited in what drills he can participate in, leaving the coaches with a hazy plan against the Ravens and their rugged defense.
He's been wearing a brace since returning to practice and has gradually become involved in more drills. He's also eager to show everyone what he can do after signing a six-year, $63 million contract in the offseason.
Information from ESPN.com's John Clayton, ESPN's Adam Schefter and The Associated Press was used in this report.