Cassel, who sustained a concussion three weeks ago in a 9-6 loss against Baltimore, sat out the Chiefs' last game on Oct. 14 -- a 38-10 loss at Tampa Bay.
The team had a bye week last weekend.
Crennel named Quinn as the starter quarterback for Sunday's game against Oakland in hopes of breaking a three-game losing streak that has seen the Chiefs' record fall to 1-5.
Cassel had been criticized for poor play prior to the concussion, managing to complete just 58.5 percent of his passes for 1,150 yards with five touchdowns and nine interceptions.
Chiefs fans drew criticism for cheering when Cassel was helped off the field following the injury.