Before becoming the Ducks' head coach, Helfrich was their quarterbacks coach and offensive coordinator from 2009-12 under Chip Kelly.
It's safe to assume that several of Fangio's defensive assistants will also return, but the Bears now have their main assistants locked in with Fangio, offensive coordinator Mark Helfrich and Special Teams Coordinator Chris Tabor.
Still, the Bears and Nagy were eager to retain Fangio, who inherited one of the NFL's worst defenses in 2015 and coached the unit back to respectability over the course of three seasons.
Helfrich was a 37-16 in his four seasons leading OR, including a Rose Bowl victory and national championship appearance in January 2015.
Helfrich is Nagy's fourth reported coaching hire and the first without ties to Lovie Smith's Bears staff.
Hiestand returned to the Bears after stints at the University of Tennessee (2010-11) and Notre Dame (2012-17).
Helfrich took the Ducks to the national title game in his second season, something that gets glossed over by critics who give the credit to quarterback Marcus Mariota.
LAKE FOREST, Ill. (AP) - The Chicago Bears have hired former OR coach Mark Helfrich as their offensive coordinator. He was sacked on the heels of a 4-8 finish in 2016.
The development of Trubisky, the No. 2 overall draft pick last spring, could go a long way toward lifting an offense that ranked 30th overall and last in passing.
Chicago also interviewed McDaniels, Philadelphia quarterbacks coach John DeFilippo, New England offensive coordinator Pat Shurmur, Vikings defensive coordinator George Edwards and Chicago defensive coordinator Vic Fangio. He was an offensive assistant with the Bears from 2007-09.
The Bears were the first team to strike with their head coach and were able to put together a nice staff because of it.