He previously served as the defensive coordinator for the Detroit Lions in 2020 and also served as an assistant coach for the Philadelphia Eagles, Denver Broncos, Jacksonville Jaguars, Cleveland Browns, New England Patriots and San Francisco 49ers Undlin attended California Lutheran University, where he played football as a safety from 1990 to 1994.
In 2005, Undlin was hired by the Cleveland Browns as a defensive assistant under head coach Romeo Crennel.
[4] On February 4, 2018, Undlin was part of the Philadelphia Eagles coaching staff that defeated the New England Patriots, 41–33, in Super Bowl LII.
[5] On January 13, 2020, Undlin was hired by the Detroit Lions as their defensive coordinator under head coach Matt Patricia.
[8] On February 14, 2023, Undlin was hired by the Houston Texans as their defensive passing game coordinator under head coach DeMeco Ryans.