Prior to joining the Chiefs as an unrestricted free agent in 2002, Quinn spent four seasons with the Jacksonville Jaguars where he served as Mark Brunell's backup.
Originally drafted by Jacksonville in the third round (86th overall) of the 1998 NFL Draft, the 6-6, 240 pounder out of Middle Tennessee State played in 11 games for the Jaguars with three starts during his four-year stay. He completed 66 of 125 passes for 748 yards with three touchdowns and four interceptions and compiled a 1-2 record as a starter, beating Pittsburgh 21-3 in 1998.
During his tenure in Jacksonville, he led the Berlin Thunder to the 2001 World Bowl title, guiding the Thunder to a 24-17 victory over the Barcelona Dragons. He started all 10 games for the Thunder in 2001, completing 167 of 296 passes for a league-high 2,257 yards and 24 touchdowns against nine interceptions (95.3 quarterback rating). Quinn earned MVP honors in the World Bowl, completing 25 of 39 passes for 308 yards with three touchdowns and two interceptions.