Warren Moon
There’s no doubt that Moon and Kurt Warner are the two greatest undrafted quarterbacks of all time. Moon’s career was crucial because he helped to break down barriers as the first black QB to enter the Hall of Fame. He played for 23 years but he arguably held on for too long (via Yardbreaker).
The less said about his time in Kansas City the better. After all, he only played three times for the Chiefs across two seasons. It’s not even worth mentioning his passing record or his interception rate because of the sample size. It’s a shame he didn’t hang up his cleats after he left Seattle.