Quinn returned to Kansas City late Tuesday after visiting with a neurologist and informed coach Romeo Crennel that he'd been advised to avoid contact. Quinn will be able to take part in light workouts during practice, but he's been declared unfit for game action.
"I talked to him this morning, talked about his situation, and he told me what the doctor had advised," Crennel said Wednesday. "So we're going to err on the side of caution and protect the football player, so that's what it is."
Quinn was hurt early in the Chiefs' loss to Oakland on Oct. 28. He missed Thursday night's game at San Diego, when Kansas City dropped to 1-7 with its fifth straight loss.
The former first-round draft pick was brought to Kansas City to back up Cassel, who is playing on a six-year, $63 million contract. Cassel was the starter early in the season before sustaining a concussion of his own against Oakland, and then lost the job during the Chiefs' bye week.
Now, Cassel will be back under center for the second straight game. Second-year pro Ricky Stanzi, who has yet to play in a regular-season game, will serve as the backup.
"He's one play away, and I think he's excited about that possibility," Crennel said. "He's preparing every week like he's going to play."
Given the way Kansas City churns through quarterbacks, it's probably a wise idea.
Cassel was the starter last year before sustaining a season-ending injury to his throwing hand. Then the carousel started, with the Chiefs starting journeyman Tyler Palko for several games and then claiming Kyle Orton off waivers to finish out the season.
When Crennel made the permanent switch from Cassel to Quinn this season, the veteran coach said he was trying to shake up a team on the skids. The head injury just a few plays into Quinn's first true game as the starter has prevented Crennel from seeing whether it would work.
"They're not cleared until they're cleared, so you have to wait," he said. "The doctors themselves don't really know when they'll be clear of concussion symptoms. They'll test him and when he's clear - he shows no residual effects - they can say, `Ok, you're cleared."'