Wallerstedt was in his second season as defensive coordinator. He previously worked at Texas A&M in the same position.
• STAPLES: Florida hits make-or-break stretch
Texas Tech has allowed 36.7 points per game during its 2-1 start to the season. In last week's 49-28 loss to Arkansas, the Red Raiders allowed 438 rushing yards and seven touchdowns on the ground. On the season, Texas Tech has allowed 893 rushing yards, which ranks last in the nation.
Rivals' Matt Clare reports Wallerstedt was fired because of "off-field issues with assistants and personal issues."
Outside linebackers coach Mike Smith is expected to replace Wallerstedt, according to FoxSports.com.
- Paul Palladino