(Official Media Release)
The decision was announced after a meeting between the two Tuesday night.
"We want to thank Mark for his eight years with the University of Oregon and appreciate his efforts on behalf of Oregon football," Mullens said. "We wish Mark and his family the best."
Helfrich coached the Ducks to a 37-16 record after taking over from Chip Kelly in 2013. After reaching the College Football Playoff championship game after the 2014 regular season, the Ducks fell to 9-4 in 2015 and then 4-8 this season, which ended Saturday in Oregon's first loss to Oregon State in nearly a decade.
"It is a great honor to have served as the head football coach at the University of Oregon," Helfrich said. "It is with respect and disappointment that we receive this decision. Plain and simple — we didn't win enough games this season.
"Thank you first to my wife, Megan, and our family, the fans, the campus community, the board, our donors and administration. To our coaches, staff and their families, it is impossible to communicate my gratitude for the environment we got to work in every single day.
"Finally, to the players — thank you, and I love you. The future is bright for this young, talented team, and we will be supporting them and their new leadership."
After taking over for Kelly following four seasons as offensive coordinator, Helfrich maintained Oregon's status as one of the nation's most potent offenses. But after finishing 37th in the FBS in total defense in 2013, the Ducks slipped to No. 89 during the playoff season, No. 117 in 2015 and No. 126 this season, despite the hiring of a new coordinator who installed a new scheme.
The Ducks saw several significant streaks end in 2016, including their winning streak in the Civil War. Oregon failed to make a bowl and suffered a losing season for the first time since 2004, and saw an Autzen Stadium sellout streak that began in 1999 end at 110 consecutive home games. The Ducks lost at least eight games for the first time since 1991.
Helfrich helped recruit and groom quarterback Marcus Mariota, who won the 2014 Heisman Trophy while leading the Ducks to the title game. But the Ducks had to rely on graduate transfers entering both 2015 and 2016.
Vernon Adams Jr. helped Oregon reach the 2015 Alamo Bowl but was hurt just before halftime, and could only watch as the Ducks squandered a 31-0 lead. Dakota Prukop won twice to open 2016 before giving way to true freshman Justin Herbert in the midst of an ensuing five-game losing streak.
Oregon's first loss of 2016 was at Nebraska, a 35-32 defeat in which the Ducks went for two after all five of their touchdowns and converted once. The next week, Pac-12 play began with a loss to Colorado in which the Ducks allowed 41 points and threw an interception on a potential game-winning TD pass in the final minute.
The recently completed season also included one-sided losses to Washington (70-21), Southern California (45-20) and Stanford (52-27). An upset of No. 11 Utah on Nov. 19 kept alive Oregon's hopes of making a bowl despite a 5-7 record, but the loss in Corvallis ended that.