Chiefs coach Romeo Crennel said on Thursday Cassel had not been cleared by doctors after suffering the injury during the fourth quarter of Kansas City's 9-6 loss to the Baltimore Ravens four days ago.
"He's excited about this opportunity," Crennel told reporters about the 27-year-old Quinn who was a first-round draft pick by the Cleveland Browns and has also played for the Denver Broncos.
"I think he'll be good and make the best of it. Quinn has been in the league, and he's been on different teams and he's seen different operations and how things are done.
"They have similar skill sets," Crennel said when asked to contrast Quinn with 2010 Pro Bowl selection Cassel. "They're both tall quarterbacks. They're both experienced. The thing that Matt has is more game time. That's the biggest difference."
Kansas City have made a stumbling 1-4 start to the season and prop up the bottom of the American Football Conference West standings.