"He's feeling a lot better, doing a lot better," Crennel said of Quinn, who has sustained two concussions this season. "He went to the doctor and he told him he's doing a lot better. The doctor also told him he was going to monitor him this week, and if he makes it through this week without incident, he could be cleared for the weekend. But he's got to make it through the week."
Cassel will start his third consecutive game. He was the starter earlier this year before sustaining his own concussion in a game against Baltimore. Quinn was the fill-in starter for a game, and then got the permanent job, only to be knocked out of his second start against the Raiders.
Quinn has been practicing, but Crennel said he's not been cleared for full contact.
"Brady does feel better. I'm glad he's feeling better. But he hasn't been cleared to play yet," Crennel said. "I can't take the chance on practicing the guy and not having him ready."
Quinn admitted last week that he tried to play through the latest concussion, which he believes happened when an Oakland defender's knee collided with the back of his helmet while he was scrambling early in the game. Quinn was later sacked, and then threw an interception during which he recalled having "tunnel vision," before he was removed from the game.
Quinn has been consulting with Dr. Micky Collins, the executive director of the UPMC Sports Medicine Concussion Program in Pittsburgh, one of the leading experts in the diagnosis, treatment and rehabilitation of athletes who have suffered concussions. Collins helped design the ImPACT test now used by many professional sports leagues, including the NFL, to assess concussions and determine when an injured athlete can safely return to play.
Crennel said that the Chiefs training staff has been relaying information to Collins, and together they'll make a determination by Sunday whether Quinn is available.
"If there are any complications, they will not clear him," Crennel said.
Cassel is on pace to have arguably the worst season of his career.
He's completing 58 percent of his throws with a quarterback rating of 66.6, and has only thrown six touchdown passes with 12 interceptions. The most recent pick, early in overtime Monday night, gave the Steelers a chip-shot field goal to win the game.
It was the Chiefs' sixth straight defeat.
"We need to build on the effort, energy and attitude we played with Monday night," Crennel said. "We have to show consistency in all areas going forward. Nobody is happy with our record."