9. Steve Spagnuolo
Steve Spagnuolo is still with Reid today, but he took a foray into head coaching following his first stint with Reid. He served as various defensive position coach from 1999-2006, before getting his first chance as a defensive coordinator in 2007.
The St. Louis Rams hired Spagnuolo as their head coach in 2009 and the results were terrible. The Rams went 1-15 in his debut season and had three consecutive losing seasons under his lead. Spagnuolo totaled a 10-38 record in St. Louis, then went 1-3 as an interim head coach for the Giants.
10. David Culley
I forgot about David Culley until I was doing the final rankings of Reid's coaching tree. Culley was in Philly with Reid from 1999-2012, serving as the wide receivers coach. Culley did follow Reid to Kansas City and served as the wide receivers coach there from 2013-2016.
Culley moved around the AFC after leaving Kansas City ultimately earning a head coaching job wit the Houston Texans in 2021. The team went 4-13 under Culley, matching their previous season record. The Texans' depth chart was in shambles, but Culley never had a chance in Houston.