So how do the Chiefs replace him?
Here's the void Magee creates at defensive end:
LDE: Tyson Jackson, Shaun Smith,
RDE: Glenn Dorsey, Wallace Gilberry
Magee was only active for two games this year so it's very possible that the Chiefs don't even replace his position. He was inactive even when Tyson Jackson wasn't out there so the new guy doesn't have to be a defensive end.
Here are the Chiefs options:
Sign someone off the street: Tuesdays are generally the day you see free agent workouts. Maybe the Chiefs worked someone out today and they'll sign them. This person would be coming to the active roster which means they'd need to get acclimated quickly. Someone with ties to the Haley/Weis/Crennel system could come into play.
Elevate someone from the practice squad: Here's the practice squad: WR Quinten Lawrence, DE Dion Gales, RT Bobby Greenwood, G Darryl Harris, QB Tyler Palko, DB Ricky Price, WR Verran Tucker, LB Pierre Walters. Lawrence and Gales spent time on the active roster last year so those would be my top two.