Christensen was formerly the assistant head coach and offensive coordinator for the University of Missouri. He served as an offensive assistant under Gary Pinkel for 19 years, including the last 16 as his offensive coordinator. He first joined Pinkel at the University of Toledo in 1990 as offensive line coach, and was promoted to offensive coordinator in 1992. Pinkel left for Missouri in 2001, and brought Christensen along as his offensive coordinator. From 2005–2008, Christensen employed a passing-oriented version of the no-huddle spread offense. In the 2007 season, Christensen's offense used this scheme to good effect by scoring a school record 558 points. Additionally, Missouri ranked fifth in total offensive yards, eighth in scoring offense, and ninth in passing yards. The same season propelled Chase Daniel to Heisman finalist status. Martin Rucker and Jeremy Maclin were named consensus All-Americans, making it the first time two Tigers were named as such in the same season. Christensen himself was a finalist for the Broyles Award and Rivals.com named him as the Offensive Coordinator of the Year. Christensen's name had been mentioned with respect to the head coaching position of several ailing programs, namely, New Mexico, Washington, Washington State, and Wyoming,. He ultimately accepted the head coaching job at Wyoming. Christensen led the Cowboys to a 2009 New Mexico Bowl win in 2009 against the Fresno State. On October 13, 2012; Christensen confronted Air Force coach Troy Calhoun after the Cowboys' narrow 28-27 loss to the Falcons. Believing Calhoun had told Air Force quarterback Connor Dietz to fake an injury in order to buy more time before the game-winning touchdown, Christensen launched a profanity-laced tirade at Calhoun, calling him a "fly boy." Christensen apologized the next night and was reprimanded by the Mountain West Conference for his actions. On October 22, Wyoming athletic directorTom Burman suspended Christensen for the Cowboys' game against Boise State and fined him $50,000. Assistant head coachPete Kaligis coached the team in that game.
Head coaching record
College
* Christensen was suspended for the Boise State game on October 27 for his actions in the Air Force game on October 20. Assistant head coach Pete Kaligis served as interim coach for the Boise State game. Wyoming credits the entire 2012 season to Christensen.